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Electronics => Projects, Designs, and Technical Stuff => Topic started by: Noopy on June 10, 2020, 07:42:33 pm

Title: Opamps - Die pictures
Post by: Noopy on June 10, 2020, 07:42:33 pm

Hi all,

if you are interested in more opamp die pictures I can post them here.


Till know I have taken pictures of a


Raytheon LM318
(https://www.richis-lab.de/images/Opamp/05x02.jpg)
https://www.richis-lab.de/Opamp05.htm (https://www.richis-lab.de/Opamp05.htm)

Thomson LM318
(https://www.richis-lab.de/images/Opamp/06x02.jpg)
https://www.richis-lab.de/Opamp06.htm (https://www.richis-lab.de/Opamp06.htm)

Sescosem SFC2741
(https://www.richis-lab.de/images/Opamp/07x03.jpg)
https://www.richis-lab.de/Opamp07.htm (https://www.richis-lab.de/Opamp07.htm)

Signetics NE5534
(https://www.richis-lab.de/images/Opamp/01x03.jpg)
https://www.richis-lab.de/Opamp01.htm (https://www.richis-lab.de/Opamp01.htm)

 :popcorn:
Title: Re: Opamps - Die pictures
Post by: magic on June 10, 2020, 08:25:26 pm
Coincidence: LM318 actually has a somewhat similar three stage topology to NE5534, although it may be hard to see it in this jungle of a schematic.
Capacitors are also connected in the same way, only one is not used (or perhaps not included in the datasheet). National's "Linear Brief" LB-17 explains a few things about this design.

Did you have some particular interest in this chip or just opened it because somebody from the forum sent you one?

Many precision amps like OP-07 or LT1028 (LT1115 is at Zeptobars) also use similar three stage topologies with similar compensation. LM118/318 was the first as far as I know.

BTW, those "adjustable" resistors appear to be simply pinch resistors. This has nothing to do with adjustments or precision of any kind, their tolerance is quite poor actually, but everything to do with producing high resistance on minimum die area.
Title: Re: Opamps - Die pictures
Post by: Noopy on June 10, 2020, 08:34:49 pm
Coincidence: LM318 actually has a somewhat similar three stage topology to NE5534, although it may be hard to see it in this jungle of a schematic.
Capacitors are also connected in the same way, only one is not used (or perhaps not included in the datasheet). National's "Linear Brief" LB-17 explains a few things about this design.

Interesting!  :-+


Did you have some particular interest in this chip or just opened it because somebody from the forum sent you one?

The opamps just appeared in my inbox.  ;D


BTW, those "adjustable" resistors appear to be simply pinch resistors. This has nothing to do with adjustments or precision of any kind, their tolerance is quite poor actually, but everything to do with producing high resistance on minimum die area.

I agree with you principally.
I speculated whether Raytheon changed the length of the overlay to adjust the resistors. Indeed not very accurate...
Title: Re: Opamps - Die pictures
Post by: Noopy on June 11, 2020, 06:31:59 am
Two more words about the suspected adjustable resistors.
Since they are pinch resistors they are commonly not very accurate. Anyway one can speculate whether Raytheon had a possibility to tune them (by mask modification perhaps).
It seems not plausible that Raytheon puts the least accurate resistors in places where they originally wanted the most accurate.
Title: Re: Opamps - Die pictures
Post by: David Hess on June 11, 2020, 11:55:49 am
Coincidence: LM318 actually has a somewhat similar three stage topology to NE5534, although it may be hard to see it in this jungle of a schematic.

...

Many precision amps like OP-07 or LT1028 (LT1115 is at Zeptobars) also use similar three stage topologies with similar compensation. LM118/318 was the first as far as I know.

Unlike those, the 318 uses emitter degeneration to lower transconductance of the first stage allowing better frequency response but this increases noise and drift making it unsuitable for audio and precision applications.  I think it was the first commercial integrated operational amplifier suitable for video applications.
Title: Re: Opamps - Die pictures
Post by: magic on June 11, 2020, 06:27:14 pm
Two more words about the suspected adjustable resistors.
Since they are pinch resistors they are commonly not very accurate. Anyway one can speculate whether Raytheon had a possibility to tune them (by mask modification perhaps).
It seems not plausible that Raytheon puts the least accurate resistors in places where they originally wanted the most accurate.
Yes, I think you're right about the tuning thing. These resistors set things like input/output stage bias currents, etc. Apparently some production variation didn't bother them too much.

I thought they simply used this slashed resistor symbol to indicate pinch resistors for whatever reason, but that's clearly not the case. There are pinch resistors drawn normally on the schematic and there is a resistor drawn with a slash which is not a pinch resistor (R2).

BTW, this is not Raytheon's schematic. Get the original from National, it has component numbers and typical values :-+
Raytheon also cheated in the bias circuit and R2 doesn't even exist in their version, but it exists on the Thomson.

Unlike those, the 318 uses emitter degeneration to lower transconductance of the first stage allowing better frequency response but this increases noise and drift making it unsuitable for audio and precision applications.
So does Douglas Self, though not as much.
Noise seems about on par with RC4558 which often successfully passes as NE5532 on AliBay :) 10~15nV/rtHz isn't terribly bad for line level signals.

On the upside, open loop linearity is improved. There is even an LM318 thread on DIYAudio: somebody swore that it's good for driving an external power stage, but its own DC linearity driving a few kΩ load was reported as "between that of µA709 and µA741".
https://www.diyaudio.com/forums/solid-state/349054-lm318-distortion.html (https://www.diyaudio.com/forums/solid-state/349054-lm318-distortion.html)
Title: Re: Opamps - Die pictures
Post by: Noopy on June 12, 2020, 06:27:45 am
BTW, this is not Raytheon's schematic. Get the original from National, it has component numbers and typical values :-+
Raytheon also cheated in the bias circuit and R2 doesn't even exist in their version, but it exists on the Thomson.

You are right but since Raytheon printed this schematic in their datasheet I wanted to refer to this one.
 
Perhaps they had to change one small thing in their design to make it "legal" and selected R2.  :-/O
Title: Re: Opamps - Die pictures
Post by: magic on June 12, 2020, 07:41:44 am
The whole bias generator is missing. Look near IN+ - it's a simple 1:3 current mirror fed by that long, snaking resistor. At the beginning of the resistor there might be an emitter follower. In other Raytheon circuits the base would be connected to an n-JFET + zener reference, though I can only identify a JFET here. Not sure what's going on, but it certainly is not the real LM318 bias circuit.

Ditto with RC5534. There is a metal layer diagram in the datasheet and it has a black hole where the bias generator ought to be (left of the output transistors). Proper NE5534 bias generator contains a pair of lateral PNPs. Nothing like that is seen anywhere besides the second stage differential pair.
Title: Re: Opamps - Die pictures
Post by: Noopy on June 12, 2020, 08:37:31 am
You are right. The bias circuit is very different, less complex:

(https://www.richis-lab.de/images/Opamp/05x06.jpg)

 :-+
Title: Re: Opamps - Die pictures
Post by: David Hess on June 12, 2020, 09:38:38 pm
Unlike those, the 318 uses emitter degeneration to lower transconductance of the first stage allowing better frequency response but this increases noise and drift making it unsuitable for audio and precision applications.

So does Douglas Self, though not as much.

I should have said low noise audio like microphone amplifiers.  After the first gain stage, the added noise is irrelevant unless it limits dynamic range.

Quote
Noise seems about on par with RC4558 which often successfully passes as NE5532 on AliBay :) 10~15nV/rtHz isn't terribly bad for line level signals.

The datasheets I have show twice the broadband noise and 6 times the low frequency noise of the RC4558.

Quote
On the upside, open loop linearity is improved. There is even an LM318 thread on DIYAudio: somebody swore that it's good for driving an external power stage, but its own DC linearity driving a few kΩ load was reported as "between that of µA709 and µA741".
https://www.diyaudio.com/forums/solid-state/349054-lm318-distortion.html (https://www.diyaudio.com/forums/solid-state/349054-lm318-distortion.html)

The 318 has about twice the output current capability as common lower power parts and its high speed allows it to operate inside of a feedback loop.  In the past I have used it as a driver for these reasons.
Title: Re: Opamps - Die pictures
Post by: Noopy on June 27, 2020, 08:14:52 pm
Hi all!

Today I can show you an opamp configured to act as voltage follower:

https://richis-lab.de/Opamp08.htm (https://richis-lab.de/Opamp08.htm)

LM310 built by Silicon General


(https://richis-lab.de/images/Opamp/08x01.jpg)

(https://richis-lab.de/images/Opamp/08x04.jpg)

Schematic is taken from National Semiconductor datasheet.
It´s a differential amplifier (red) with an output stage (purple). No VAS since a voltage follower needs no voltage amplification. And with lower amplification you need less negative feedback. With less negative feedback a bigger bandwith is still stable.  :-+


(https://richis-lab.de/images/Opamp/08x03.jpg)

The die is not extremly interesting...

 :popcorn:
Title: Re: Opamps - Die pictures
Post by: magic on June 27, 2020, 09:12:56 pm
Well, one interesting thing is that the circuit uses a bunch of superbeta NPNs and it looks like there is no obvious way to tell them apart visually.

And class A output stage. Probably that's the true reason why it's so fast: no dirty PNPs in the signal path ;)
Title: Re: Opamps - Die pictures
Post by: Noopy on June 28, 2020, 05:36:17 am
You are right. There should be superbeta NPNs but as far as i know you can´t really distinguish them from "normal" NPNs. The base is just thinner…

There is a application note advertising the speed of the LM310 and explaining it with the use u NPNs.  :-+
Title: Re: Opamps - Die pictures
Post by: magic on June 28, 2020, 06:28:24 am
It's a common thing in "high speed" amplifiers built on 1970's noncomplementary processes. The 318/5534 also bypass their PNP differential stage with capacitors to yield an amplifier which is 100% NPN at high frequencies.

There is one textbook author who will want you to believe that all of these capacitors are for nested Miller feedback, ignore him and read LB-17 ;)
Title: Re: Opamps - Die pictures
Post by: Noopy on June 28, 2020, 10:08:08 am
Yes, the right mixture of negative feedback and feedforward. That's the trick.
What's LB-17?
Title: Re: Opamps - Die pictures
Post by: magic on June 28, 2020, 10:49:57 am
The NatSemi paper about LM118/318 which I mentioned before.
Title: Re: Opamps - Die pictures
Post by: Noopy on June 28, 2020, 12:05:15 pm
Of course! Sorry, I was confused somehow.  :-+
Title: Re: Opamps - Die pictures
Post by: SeanB on June 28, 2020, 12:55:45 pm
Now I know how those hundreds of SFC2741 op amps I changed over the years look like inside, thank you. most were changed because of offset drift going outside the limits that could be compensated, which was not bed after 20 years of being alternately baked and chilled.
Title: Re: Opamps - Die pictures
Post by: Noopy on June 28, 2020, 01:11:05 pm
More coming soon!  :) :popcorn:
Title: Re: Opamps - Die pictures
Post by: David Hess on June 28, 2020, 04:23:22 pm
Check out Linear Technology application note 16 (https://www.analog.com/media/en/technical-documentation/application-notes/an16f.pdf) where Widlar himself describes some details of PNPs on an NPN only process in these types of integrated circuits.
Title: Re: Opamps - Die pictures
Post by: Noopy on July 07, 2020, 08:49:17 pm
Today I have a comparator, a LM306, for you:

(https://www.richis-lab.de/images/Opamp/09x01.jpg)

(https://www.richis-lab.de/images/Opamp/09x02.jpg)

(https://www.richis-lab.de/images/Opamp/09x04.jpg)


https://www.richis-lab.de/Opamp09.htm (https://www.richis-lab.de/Opamp09.htm)


It´s a comparator, not a normal opamp. Note the difference.  :-/O :)
Title: Re: Opamps - Die pictures
Post by: Hydron on July 08, 2020, 09:53:33 pm
Love the pictures!

Have you looked at any of the more exotic modern analogue parts? Or are they normally covered with lots of metal etc, obscuring the interesting bits? I'm thinking of stuff a bit out of the ordinary like a AD8129/8130 (I assume there will be trimmed parts etc involved in one of those).
Title: Re: Opamps - Die pictures
Post by: Noopy on July 09, 2020, 03:22:27 am
That´s nice to hear!  :-+

Right at the moment I just decap the parts people have donated. Often these parts are from the older generation but basically I decap everything.
Especially in the opamp category I mostly have older parts. But I put the AD8129 on my to-do-list. Sounds interesting! :-+
Title: Re: Opamps - Die pictures
Post by: magic on July 09, 2020, 06:55:44 am
Have you looked at any of the more exotic modern analogue parts? Or are they normally covered with lots of metal etc, obscuring the interesting bits? I'm thinking of stuff a bit out of the ordinary like a AD8129/8130 (I assume there will be trimmed parts etc involved in one of those).
Perhaps not covered by lots of metal, but newer parts may use more than one metal layer which gives a bit of extra headache. You can see what it looks like on Noopy's AD587 voltage reference photos; thankfully that one had only two layers.

The amplifiers you listed certainly use a true complementary process which means NPN and PNP will be much more similar to each other.

Zeptobars probably has photographs of some more advanced analog parts.
Title: Re: Opamps - Die pictures
Post by: macboy on July 09, 2020, 01:11:33 pm
Unlike those, the 318 uses emitter degeneration to lower transconductance of the first stage allowing better frequency response but this increases noise and drift making it unsuitable for audio and precision applications.
So does Douglas Self, though not as much.
Noise seems about on par with RC4558 which often successfully passes as NE5532 on AliBay :) 10~15nV/rtHz isn't terribly bad for line level signals.

On the upside, open loop linearity is improved. There is even an LM318 thread on DIYAudio: somebody swore that it's good for driving an external power stage, but its own DC linearity driving a few kΩ load was reported as "between that of µA709 and µA741".
https://www.diyaudio.com/forums/solid-state/349054-lm318-distortion.html (https://www.diyaudio.com/forums/solid-state/349054-lm318-distortion.html)

I have an old instrument, "Precision Filters 602 Dual Anti-Alias Filter", which uses LM318H and LM301 in TO-99 cans for the analog circuitry. Measured with 80 kHz bandwidth, I measure around 3 ppm (0.0003%) THD+N. The THD only (20 harmonics) measures at 0.8 ppm (0.00008%) which is equivalent to the measurement floor of my VP-7722, so it is perhaps much less, but not higher than that. The instrument dates back to ca. 1970's.
Title: Re: Opamps - Die pictures
Post by: Noopy on July 10, 2020, 09:54:41 pm
Today I have an old LM360 for you:

(https://www.richis-lab.de/images/Opamp/10x01.jpg)

(https://www.richis-lab.de/images/Opamp/10x04.jpg)

With the same die you can build a LM361.  :-+

https://www.richis-lab.de/Opamp10.htm (https://www.richis-lab.de/Opamp10.htm)

 :popcorn:
Title: Re: Opamps - Die pictures
Post by: Noopy on July 25, 2020, 07:28:36 pm
Today I have a fake NE5534 for you:

https://www.richis-lab.de/Opamp11.htm (https://www.richis-lab.de/Opamp11.htm)

1,40€ for ten of these bugs including shipping.  :palm:


(https://www.richis-lab.de/images/Opamp/11x01.jpg)

Tried to fake a Texas Instruments Logo? I don´t know.  :-// :-DD


(https://www.richis-lab.de/images/Opamp/11x02.jpg)

The number 659 doesn´t really fit. It seems to be a RC4558.  :--

 :popcorn:
Title: Re: Opamps - Die pictures
Post by: magic on July 25, 2020, 08:04:41 pm
You were lucky ;D
I got LM358 and so did some Turkish poster here the other day.

If you are looking for recycled authentic NE5532/4 from China it may be hard. I tend to look for auctions with positive feedback and preferably including buyer's photos of the delivered ICs. Prefer auctions which show unblurred manufacturer logo. But it's still lottery - I once ordered from an auction with a real photograph of ON Semi NE5534 and got a mix of recycled chips from unknown manufacturers with fake NXP branding (NXP never made those chips). At least they weren't completely fake.

edit
Wait, why all the pads look like they had been bonded?
Did they connect the second channel's bonding pads to the compensation/balance pins?
Or is it actually a normally bonded dual opamp, not pin-compatible with single opamps and there will be smoke if somebody tries to use it?
Title: Re: Opamps - Die pictures
Post by: Noopy on July 25, 2020, 08:42:58 pm
I searched for the cheapest NE5534 to find a fake. :D

I assume it's a RC4558 with the pinout of a RC4558. Probably they recycled RC4558 and changed them to NE5534 to make more money.
Normal (NE5534) connection will probably give you magic smoke...
Title: Re: Opamps - Die pictures
Post by: magic on July 25, 2020, 08:57:48 pm
The shape of the packages looks Chinese and I found this exact die in a few different fake opamps. It's smaller than Raytheon or TI dice. It's some Chinese clone of RC4558 with fake markings.

Smarter fakers modify the pinout to be compatible with single opamps.
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=232934.0;attach=959888;image)
Title: Re: Opamps - Die pictures
Post by: Noopy on July 25, 2020, 09:07:57 pm
The shape of the packages looks Chinese and I found this exact die in a few different fake opamps. It's smaller than Raytheon or TI dice. It's some Chinese clone of RC4558 with fake markings.

That would explain why there are the numbers 659 which don't match with a RC4558.
Title: Re: Opamps - Die pictures
Post by: magic on July 25, 2020, 10:04:35 pm
Some Chinese opamps:
https://www.eevblog.com/forum/beginners/opamp-input-offsets-working-in-the-opposite-direction-to-what-i-expect/25/ (https://www.eevblog.com/forum/beginners/opamp-input-offsets-working-in-the-opposite-direction-to-what-i-expect/25/)
https://www.eevblog.com/forum/projects/whats-inside-the-cheapest-and-fakest-jellybean-opamps/ (https://www.eevblog.com/forum/projects/whats-inside-the-cheapest-and-fakest-jellybean-opamps/)
Have you really not seen those threads yet?

Yes, they sometimes incude some numbers and logos, nobody knows what they mean.
Title: Re: Opamps - Die pictures
Post by: Noopy on July 25, 2020, 10:20:09 pm
Of course I have seen those threads!  ;D
But that was some time ago and I have forgotten you already had found the numbers 659.

Nevertheless I´m not sure whether these 659-dies are conterfeits.
I know the datasheet describes the RC4558 to be bigger but zeptobars already found one smaller than that (bigger than this one here). Perhaps they did another die shrink and the opamp found here is no fake-RC4558 but a real one?
Title: Re: Opamps - Die pictures
Post by: Noopy on August 03, 2020, 03:18:07 pm
I have something for you AMD built just before they started up their 7nm-fabrication.  ;D


(https://www.richis-lab.de/images/Opamp/12x01.jpg)

(https://www.richis-lab.de/images/Opamp/12x02.jpg)


https://www.richis-lab.de/Opamp12.htm (https://www.richis-lab.de/Opamp12.htm)


Looks quite similar to the Silicon General LM310 (https://www.richis-lab.de/Opamp08.htm (https://www.richis-lab.de/Opamp08.htm)) but has some differences.  :-/O


Title: Re: Opamps - Die pictures
Post by: David Hess on August 03, 2020, 09:19:15 pm
I have something for you AMD built just before they started up their 7nm-fabrication.  ;D

Few people remember that AMD second sourced linear ICs.  I remember having to remove them as a supplier because too many parts had popcorn noise which is a processing problem.  I heard cussing over the reliability of their UVEPROMs also.
Title: Re: Opamps - Die pictures
Post by: Noopy on August 17, 2020, 06:47:27 pm
I took pictures of a OPA676 (thanks to dzseki).
That´s a very interesting opamp! It can go up to 185MHz with a slewrate of 350V/µs and it has two differential inputs which you can switch as you want.
Even more interesting: The OPA676 is integrated on an universal die. Something like an analog gatearray.

(https://www.richis-lab.de/images/Opamp/13x03.jpg)

(https://www.richis-lab.de/images/Opamp/13x09.jpg)


The two metal layers are designed by Burr-Brown. The "analog gatearray" is supplied by VTC:

(https://www.richis-lab.de/images/Opamp/13x08.jpg)

(https://www.richis-lab.de/images/Opamp/13x07.jpg)


More pictures here:

https://www.richis-lab.de/Opamp13.htm (https://www.richis-lab.de/Opamp13.htm)

 :popcorn:
Title: Re: Opamps - Die pictures
Post by: Noopy on August 20, 2020, 04:01:20 am
(https://www.richis-lab.de/images/Opamp/14x01.jpg)

Today I have a LF355 for you. This one was manufactured 1977.  :-+


(https://www.richis-lab.de/images/Opamp/14x02.jpg)

Although the LF355 is the slowest opamp of the LFx5x-family, the capacitors are not as big as possible. I assume 1977 TI wasn´t sure how big they needed the capacitors to get stable operation and because of that they made the possible capacitor area bigger...  :-/O


https://www.richis-lab.de/Opamp14.htm (https://www.richis-lab.de/Opamp14.htm)


 :popcorn:
Title: Re: Opamps - Die pictures
Post by: magic on August 20, 2020, 07:20:32 am
Damn, thank you, man. I now know what was inside my fake AD797 from AliExpress :-DD

I couldn't figure out how those input transistors work. JFET :palm:

But wait, is this a genuine LF355?
Title: Re: Opamps - Die pictures
Post by: Noopy on August 20, 2020, 07:48:00 am
At least it was an opamp! :D
Title: Re: Opamps - Die pictures
Post by: magic on August 20, 2020, 09:07:36 am
Did you get this chip from eBay?

There is no LF-anything in the 1984 Texas Instruments linear databook. There is a lot of second source LM parts, second sources of half a dozen other manufacturers, and there are TI's own TL07x JFET opamps and many other TL and TLC devices, but I can't see a single National JFET chip of any sort.

Their current datasheet SNOSBH0D dates to year 2000, FWIW.
Title: Re: Opamps - Die pictures
Post by: Noopy on August 20, 2020, 09:44:44 am
Hm, you are right, that´s strange...

I got it from Ebay and the printing is very modern and clean. That is somehow suspicious with such an old part.

But it seemed plausible. I have three different National Semiconductor LF355 here. All three have the same design with two different revisions. They look quite similar to the "TI LF355" but are not the same. It seemed quite plausible that both companys had built one.

 :-//
Title: Re: Opamps - Die pictures
Post by: magic on August 20, 2020, 10:26:19 am
Actually my chip is slightly different but I'm pretty sure it's the same LF15x circuit. Maybe one of the faster versions because the capacitors are smaller.

And there are two capacitors, I think the one near pin 4 is the compensation capacitor indicated on the schematic and the one near pin 1 is something else. One plate is connected to ground.

The large JFETs on the left appear to be the input devices, pins 1 and 5 go to another pair of structures which probably are JEFTs and I have no idea what are the transistors in the middle. Perhaps JFET constant current sinks?

I'm not sure why the connections to input JFET gates are swapped. On my chip, the IN+ JFET is near the IN+ pad and the IN- JFET is near the IN- pad.
Title: Re: Opamps - Die pictures
Post by: Noopy on August 21, 2020, 11:48:19 am
The second capacitor is connected to the non-inverting output of the differential stage. There is a more detailed schematic in a National datasheet showing this capacitor.


I now have pictures of the other LF355 (National Semiconductor). First one was built 1982:

(https://www.richis-lab.de/images/Opamp/15x01.jpg)

(https://www.richis-lab.de/images/Opamp/15x02.jpg)

(https://www.richis-lab.de/images/Opamp/15x03.jpg)

(https://www.richis-lab.de/images/Opamp/15x04.jpg)


The second one was built 1988:

(https://www.richis-lab.de/images/Opamp/16x01.jpg)

(https://www.richis-lab.de/images/Opamp/16x02.jpg)


That´s odd:

(https://www.richis-lab.de/images/Opamp/15x05.jpg)

The 1982-LF355 mask revisions were modified often.

(https://www.richis-lab.de/images/Opamp/16x03.jpg)

The 1988-LF355 shows only A-revisions.  :-//
There is also a C at the bottom of the die. The older LF355 shows an A.  :-//


Still there is the question whether the Texas-LF355 is a fake or not.  :-//
Title: Re: Opamps - Die pictures
Post by: David Hess on August 23, 2020, 03:52:12 am
Although the LF355 is the slowest opamp of the LFx5x-family, the capacitors are not as big as possible. I assume 1977 TI wasn´t sure how big they needed the capacitors to get stable operation and because of that they made the possible capacitor area bigger...  :-/O

I am sure they knew exactly how large to make the capacitors.

JFETs have lower transconductance at the same current than bipolar transistors so a smaller compensation capacitor is required yielding a higher slew rate.  Bipolar parts get the same advantage by using transconductance reduction which is why the 741 compensation capacitor is several times larger than later 741 replacements like the MC1458 which use transconductance reduction for exactly this reason.  Transconductance reduction is also what made the 324 so economical; its compensation capacitor is tiny.

So early JFET parts had an inherent size, and therefor cost, advantage over early bipolar parts because they had smaller compensation capacitors.
Title: Re: Opamps - Die pictures
Post by: Noopy on August 23, 2020, 06:34:52 am
But that doesn't explain why the capacitor area is bigger than actually necessary.
If they had known exactly how big the capacitance had to be, they would have integrated the right size and saved the area as in the National Semiconductor LF355.
I'm pretty sure they didn't use the same die for a bipolar opamp...
Title: Re: Opamps - Die pictures
Post by: magic on August 23, 2020, 07:41:58 am
JFETs have lower transconductance at the same current than bipolar transistors so a smaller compensation capacitor is required yielding a higher slew rate. Bipolar parts get the same advantage by using transconductance reduction
If you mean that LM324 trick of discarding 75% of the input stage current to ground, then no, not exactly the same. Mind that LM324 is the worst opamp in the world in terms of slew rate, besides ultra low power stuff.

IMO "transconductance reduction" is a big misnomer. In practice, it's just reduction of the input stage current as seen by the VAS, with all the usual consequences: lower gain, higher noise, lower slew rate. I don't know what was the supposed advantage of that over simply making these transistors 4x smaller and running them at 25% current. I can guess that maybe they couldn't make them small enough and the additional grounded collector and additional bias were necessary to clear the base of stored charge acceptably fast.

which is why the 741 compensation capacitor is several times larger than later 741 replacements like the MC1458 which use transconductance reduction for exactly this reason.
Not sure if they do, certainly not Raytheon. They conveniently provided schematics of most of their analog parts and specified 25pF on both versions. Their die photographs don't indicate significant difference in capacitor area either. The RC1458 seems more efficiently packed with less wasted space, though, and its die is only 50% larger.

So early JFET parts had an inherent size, and therefor cost, advantage over early bipolar parts because they had smaller compensation capacitors.
Well, for the record, this LF155 die is huge because of all those silly JFETs whose function could be replicated with 5x smaller bipolars ;) But there are much better JFET opamps out there, like TL072, which packs two channels on about the same area IIRC.

I lost my LF155, maybe Noopy could post exact dimensions?
Title: Re: Opamps - Die pictures
Post by: Noopy on August 23, 2020, 07:56:26 am
I lost my LF155, maybe Noopy could post exact dimensions?

~ 1,87mm x 1,06mm

 :-+
Title: Re: Opamps - Die pictures
Post by: David Hess on August 25, 2020, 11:10:58 am
I don't know what was the supposed advantage of that over simply making these transistors 4x smaller and running them at 25% current.

As explained on page 19 of National Semiconductor application note A, reducing the current to reduce the transconductance also reduces phase margin from the mirror pole and the tail pole, so in that case the compensation capacitance must be *increased* to reduce bandwidth maintaining stability.

https://web.ece.ucsb.edu/Faculty/rodwell/Classes/ece2c/resources/an-a.pdf

Quote
which is why the 741 compensation capacitor is several times larger than later 741 replacements like the MC1458 which use transconductance reduction for exactly this reason.

Not sure if they do, certainly not Raytheon. They conveniently provided schematics of most of their analog parts and specified 25pF on both versions. Their die photographs don't indicate significant difference in capacitor area either. The RC1458 seems more efficiently packed with less wasted space, though, and its die is only 50% larger.

Schematics are usually simplified to not show the transconductance reduction, including the Raytheon RC1458 datasheet I just checked, and I suspect the 741 schematic and values were used instead.  Could a process difference explain the capacitor area you saw?  What really matters is the difference so a 741 on the same process should be compared.

I thought I saw an MC1458 schematic which showed a much lower value of compensation capacitor but now I cannot find it.  Hmm, maybe I was thinking of what sure looks like the MC1458 schematic shown on page 20 of the application note linked above which indicates 5 picofarads instead of the customary 30 picofarads.
Title: Re: Opamps - Die pictures
Post by: magic on August 25, 2020, 01:49:31 pm
So there are three schemes described in this appnote: figure 27, 28a and 28b.

They admit that 28a has a problem with increased noise and 28b may be difficult to fabricate accurately at high "reduction ratio".

Figure 27 could in theory be implemented sneakily in lateral PNP input stages, by increasing parasitic collection by the substrate (which normally is undesirable and efforts are made to prevent it), so you could look at a die and never know that a deliberately introduced, significant substrate collector is there.

But the figure 28 schemes are impossible to realize without additional surface collectors and metal traces hooking them up to the mirror and/or ground. So if a chip exists which uses an "advanced" scheme, we could find it, tear it down and see it. So far I haven't seen anything like that. Not in several 358s, not in the RC4558 from Zeptobars and in Chinese RC4558, not in NJM2068 (a Japanese 4558 on steroids), not in the numerous voltage references posted in "metrology". Nor in this LF155 or TL072, for that matter. If these schemes are used, they probably aren't that very common.

This leaves us with the figure 27 scheme, which is hard to disprove by eyeballing because of the aforementioned possibility of a hidden substrate collector. But we can look at its noise implications. Protest if you think I'm wrong, but I'm quite convinced that noise performance of such input stage is simply equivalent to a normal stage running on n-times reduced bias. I will ignore mirror contribution (imagine that it's sufficiently degenerated or whatever) and look at the LTP.

If I got my math right, transconductance of a mirror loaded LTP equals transconductance of each individual transistor. Noise of an undegenerated BJT happens to be equivalent to the Johnson noise of half its intrinsic emitter resistance (which doesn't have real Johnson noise, obviously), and therefore noise of an LTP conveniently equals the "Johnson" noise of 1/gm. And 1/gm happens to be the reactance of Cc at unity gain frequency, so our math is surprisingly easy.

Take a normal 741 with Cc=25~30pF and GBW=1MHz. That's some 5.5~6kΩ impedance and therefore a hair under 10nV/rtHz LTP noise. Multiply by 1.4 because of the NPN emitter followers and we are at 14nV/rtHz. A real 741 has a hair over 20nV/rtHz IIRC.

Now take the "improved" 741 with 5pF. That's 32kΩ and 22nV/rtHz, even before the 1.4x factor. It simply cannot meet the original spec.

Curiously, Raytheon specifies RC1458 noise similarly to 741, but Motorola's MC1458 density plot shows 40nV/rtHz. Hmm... that puppy may need a teardown.
Title: Re: Opamps - Die pictures
Post by: Noopy on August 26, 2020, 08:24:17 pm
A little bit more modern: LF411

(https://www.richis-lab.de/images/Opamp/17x01.jpg)

(https://www.richis-lab.de/images/Opamp/17x02.jpg)

Sorry, have no size for this one.


(https://www.richis-lab.de/images/Opamp/17x04.jpg)

It seems that the upper five testpads are used to adjust the absolute value of the offset while the lower three testpads change the polarity of the value. Interesting...
By the way: That´s an interesting transistor type!


(https://www.richis-lab.de/images/Opamp/17x03.jpg)

The LF411 has four cross connected JFETs at the input.
Nevertheless the offset of the LF411 is a bit higher (7µV/°C typ) than the LF355 (5µV/°C typ)!  :o
I assume the higher integration of the LF411 leads to more temperature depending drift.
Title: Re: Opamps - Die pictures
Post by: magic on August 26, 2020, 09:18:14 pm
more modern: LF411
:D

By the way: That´s an interesting transistor type!
You bet.
[attachimg=1]
Title: Re: Opamps - Die pictures
Post by: Noopy on September 23, 2020, 06:00:48 pm
One more "normal" Opamp, a OP-01:

https://www.richis-lab.de/Opamp18.htm (https://www.richis-lab.de/Opamp18.htm)


(https://www.richis-lab.de/images/Opamp/19x01.jpg)

If you have read my DAC-posts you know the OP-01 from DAC80 and DAC800.
BTW: If you support me on patreon you get a free newsletter! https://www.patreon.com/richis_lab (https://www.patreon.com/richis_lab) ;)


(https://www.richis-lab.de/images/Opamp/19x02.jpg)

(https://www.richis-lab.de/images/Opamp/19x03.jpg)

A nice design...


(https://www.richis-lab.de/images/Opamp/19x04.jpg)

Here you can see how the differential signal is processed in a crisscross way in the input stage. With this arrangement thermal gradients cause contrary drifts that cancel each other out (of course not perfectly). PMI called it "thermally cross-coupled quad".
Title: Re: Opamps - Die pictures
Post by: mawyatt on September 23, 2020, 06:59:10 pm
One more "normal" Opamp, a OP-01:

https://www.richis-lab.de/Opamp18.htm (https://www.richis-lab.de/Opamp18.htm)


If you have read my DAC-posts you know the OP-01 from DAC80 and DAC800.

A nice design...


(https://www.richis-lab.de/images/Opamp/19x04.jpg)

Here you can see how the differential signal is processed in a crisscross way in the input stage. With this arrangement thermal gradients cause contrary drifts that cancel each other out (of course not perfectly). PMI called it "thermally cross-coupled quad".

George Erdi invented this technique, another brilliant linear IC designer like Bob Widlar. Not only helps with thermal gradients, but also process & stress gradients!!

Best,
Title: Re: Opamps - Die pictures
Post by: magic on September 23, 2020, 07:52:54 pm
The latter only if they affect NPN and PNP in the same way. Dunno if it's the case in practice.

If you like that kind of mazes, try OP07 once ;)
Title: Re: Opamps - Die pictures
Post by: David Hess on September 23, 2020, 08:06:14 pm
Didn't the early precision parts like the OP-05 and OP-07 use a quad of quads?  I have seen various layouts extending to 8 or 16 cross coupled transistors.
Title: Re: Opamps - Die pictures
Post by: Noopy on September 23, 2020, 08:14:47 pm
(https://richis-lab.de/images/DAC/09x21.jpg)

OP-07  :-+


(https://richis-lab.de/images/DAC/09x17.jpg)

OP-27, also nice!  :-+


Both use quite a lot transistors.


...taken from AD1139:
https://richis-lab.de/DAC07.htm (https://richis-lab.de/DAC07.htm)
Title: Re: Opamps - Die pictures
Post by: David Hess on September 23, 2020, 08:28:30 pm
Both use quite a lot transistors.

And a lot of area for capacitors.

Also notice how the output transistors on one side of the die are lined up with the input transistors on the other side.

Title: Re: Opamps - Die pictures
Post by: mawyatt on September 24, 2020, 06:55:54 pm
Didn't the early precision parts like the OP-05 and OP-07 use a quad of quads?  I have seen various layouts extending to 8 or 16 cross coupled transistors.

Think Erdi came up with the single cross coupled quad concept either at Fairchild or PMI, but don't know about the more complex input transistor layouts.

Best,
Title: Re: Opamps - Die pictures
Post by: mawyatt on September 24, 2020, 07:08:28 pm
Both use quite a lot transistors.

And a lot of area for capacitors.

Also notice how the output transistors on one side of the die are lined up with the input transistors on the other side.


Lining up the output with input transistors helps create a more uniform thermal gradient wavefront across the chip.

A fun story along these lines was when the IEEE was debating whether a high current 5 Volt linear regulator for TTL logic could be integrated on a single chip. Thermal feedback was what the debate was all about, so they decided to ask Bob Widlar what he thought. The story goes Wilder said, "Of course you can't make a high current 5 Volt single chip linear regulator, thermal feedback will completely mess things up, are you guys completely nuts!!", or something like that. >:D

A few months later National introduced the 1st high current 5 Volt Linear Regulator chip :-DD

Best,
Title: Re: Opamps - Die pictures
Post by: David Hess on September 24, 2020, 11:17:36 pm
Thermal feedback is also what limits open loop gain of a monolithic operational amplifier, so the symmetrical layout and thermal balancing also increase open loop gain.  This is why it is important to minimize loading on precision operational amplifiers, and why the highest precision parts are also lower power.
Title: Re: Opamps - Die pictures
Post by: mawyatt on September 24, 2020, 11:48:42 pm
I remember seeing an open loop plot of a certain brand 741 op amp that showed the thermal feedback actually caused the + and - inputs to reverse :o

Of course this would normally be squashed by massive external negative feedback, but still not a good op amp parameter :P

Best,
Title: Re: Opamps - Die pictures
Post by: mawyatt on September 24, 2020, 11:57:05 pm
(https://richis-lab.de/images/DAC/09x21.jpg)

OP-07  :-+


(https://richis-lab.de/images/DAC/09x17.jpg)

OP-27, also nice!  :-+


Both use quite a lot transistors.


...taken from AD1139:
https://richis-lab.de/DAC07.htm (https://richis-lab.de/DAC07.htm)

Thanks for showing, the OP-07 is my favorite precision GP op-amp, really a well behaved and precise device.

Best,
Title: Re: Opamps - Die pictures
Post by: David Hess on September 25, 2020, 12:07:07 am
I remember seeing an open loop plot of a certain brand 741 op amp that showed the thermal feedback actually caused the + and - inputs to reverse :o

Of course this would normally be squashed by massive external negative feedback, but still not a good op amp parameter :P

In precision applications, the thermal time constant can increase settling time, and may provide the largest contribution to it.

Thanks for showing, the OP-07 is my favorite precision GP op-amp, really a well behaved and precise device.

My favorite is the LT1008/LT1012/LT1097 because of its even lower input bias current.
Title: Re: Opamps - Die pictures
Post by: Noopy on October 14, 2020, 06:59:16 pm
(https://richis-lab.de/images/Opamp/20x01.jpg)

OP-283
Two Opamps, 5MHz bandwith, single supply 3V-36V, 25mA/30mA output current. The datasheet states the OP-283 as a good microphone and earphone amplifier.


(https://richis-lab.de/images/Opamp/20x02.jpg)

The structures are quite symmetrical but the bondpads are not placed perfectly.
The offset of the mono-opamp OP-183 is laser trimmed. The OP-283 contains two complex resistor areas at the bottom of the die which contain the collector resistors. Probably these resistors are laser trimmed.  :-/O


(https://richis-lab.de/images/Opamp/20x03.jpg)

A lot of signatures? Crowns for the developers? OK...  ;D


https://richis-lab.de/Opamp19.htm (https://richis-lab.de/Opamp19.htm)

Title: Re: Opamps - Die pictures
Post by: magic on October 14, 2020, 08:47:54 pm
Interesting way of doing phase summing, it seems they feed input stage currents into the emitters rather than collectors of a current mirror.

Not sure if it really is that great for audio, but likely better than a certain jellybean single supply opamp ;)
Title: Re: Opamps - Die pictures
Post by: Noopy on October 14, 2020, 09:05:23 pm
Interesting way of doing phase summing, it seems they feed input stage currents into the emitters rather than collectors of a current mirror.

Q3/Q4?
That´s a common base amplifier, right? Good for voltage amplification. Sound like a good solution for a VAS if you add some current amplification? *brainstorming*


Not sure if it really is that great for audio, but likely better than a certain jellybean single supply opamp ;)

Well at least it sounds good in a datasheet.  ;D
Title: Re: Opamps - Die pictures
Post by: magic on October 14, 2020, 09:50:47 pm
Q3/Q4?
That´s a common base amplifier, right? Good for voltage amplification. Sound like a good solution for a VAS if you add some current amplification? *brainstorming*
Q4 might be consider common base but it doesn't do voltage amplification. It feeds current into the base of Q6 which is roughly constant at two diode drops above the negative rail. Q6 drives Q10 which is the VAS and Q11.

Q3 might be seen as common base too, but it operates in a tight negative feedback loop: increasing Q3 current instantly pulls down Q5 which turns off Q3 base and reduces its current. In fact, Q3 current is almost constant, determined by QB7. Q3 and Q5 simply shift R3 voltage one diode up and apply it to Q4 base, whose emitter applies the original R3 voltage across R4.

This way current variations in Q1 are transferred to the Q2 side. And then Q4 feeds that current imbalance into Q6. That's how I see it.

QB7 and QB8 are of course constant sources. Not sure what's the point of Q7 and Q8 because it seems that Q5 and Q6 collectors could simply be connected to VCC. Maybe something to do with phase reversal prevention or a trick to improve open loop linearity. I don't know, that would take some actual thinking :)
Title: Re: Opamps - Die pictures
Post by: Noopy on October 15, 2020, 03:03:18 am
...

Sounds reasonable, thanks!  :-+
Title: Re: Opamps - Die pictures
Post by: P_Doped on October 15, 2020, 11:16:08 pm
I'm assuming this portion of the discussion is about these transistors in the simplified schematic inside the OP07 datasheet.

If so, my guess is that Q3-Q8 are there to perform input bias current cancellation.

If you go around the loop on 1 side, say the inverting input:
Q2 requires base current (call it Ib2).  Q4 is in the collector path of Q2 to "sample" it and create a replica of Ib2 in its base current since they are both NPN transistors.

I'm assuming Q8 is a PNP like Q6.  Bipolar people love to draw diode connected bipolars as diodes.  Assume Q8 is a diode connected PNP. 
Since they both have the same Veb and the same characteristics, they contribute into that common node a current, (beta+2)*Ib6 (Ib6 from Q6 and (beta+1)*Ib8 from Ib8 and Q6 & Q8 are matched with the same Veb, so Ib8 = Ib6).  That has to equal the replica base current of Q4.

So, we have Ib6 = Ib4/(beta+2) = Ib2/(beta+2).

Q6's collector current, Ic6, is beta*Ib6 = beta/(beta+2) * Ib2 ~ Ib2.

Now you've injected a current into the inverting input of approximately the same value as the actual input current creating a nice cancellation.

I may be a bit off, but I think that's the basic idea.
Title: Re: Opamps - Die pictures
Post by: Noopy on October 16, 2020, 03:07:49 am
We are talking about the 183 shematic printed here:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjuk6qPjbjsAhWjM-wKHf9lBaIQFjAAegQIBBAC&url=https%3A%2F%2Fwww.analog.com%2Fmedia%2Fen%2Ftechnical-documentation%2Fobsolete-data-sheets%2F397961741OP283.pdf&usg=AOvVaw1Ul7ZkuV70TxPg6yv7QM27 (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjuk6qPjbjsAhWjM-wKHf9lBaIQFjAAegQIBBAC&url=https%3A%2F%2Fwww.analog.com%2Fmedia%2Fen%2Ftechnical-documentation%2Fobsolete-data-sheets%2F397961741OP283.pdf&usg=AOvVaw1Ul7ZkuV70TxPg6yv7QM27)

 :-/O


...but I didn´t understand everything of your OP07-calculation...
Have to think about that...
Title: Re: Opamps - Die pictures
Post by: magic on October 16, 2020, 06:56:17 am
If so, my guess is that Q3-Q8 are there to perform input bias current cancellation.
In the OP07, yes, but see above ;)

There is a die photograph of OP07 a few posts above, you can see that this is pretty much exactly how it works.

There is yet another level of bootstrapped cascode over Q3,Q4 before the signal gets to the emitter followers driving the second stage. I presume it's because otherwise Early effect would break bias cancellation accuracy over input common mode range and reduce input resistance.

Q7,Q5 and Q8,Q6 are two 50:50-ratio split collector lateral PNPs above and below the input cascode block and one collector of each (the input) is also connected to base. Classic IC current mirror trick.
Title: Re: Opamps - Die pictures
Post by: capt bullshot on October 16, 2020, 07:14:14 am
Q3/Q4?
That´s a common base amplifier, right? Good for voltage amplification. Sound like a good solution for a VAS if you add some current amplification? *brainstorming*


Had a quick glance at the schematic, didn't go into details as you did.
To me, Q3/Q4 just look like a folded cascode configuration with the input transistors.
Title: Re: Opamps - Die pictures
Post by: magic on October 16, 2020, 07:19:52 am
Folded cascode would have its bases held at constant voltage and collectors loaded with a mirror rather than a pair of equal, stiff current sources. But it's a similar thing in principle, I think.

Here those "cascode" transistors track voltage across R3 and transfer it to R4. At some high frequency, parallel capacitance across R3 kills those voltage swings to eliminate phase delay through the phase summing circuit from the amplifier's forward path, apparently.

edit
Okay, I will try more clearly. In a classic folded cascode amplifier, Q3 transfers Q1 current swings to a PNP mirror above and phase summing occurs between the output of said mirror and Q4. Here, phase summing occurs between R4 and Q4 and Q4 is just a cascode over that node, while the Q3,Q5 circuit is basically a voltage follower, with +1Vbe offset rather than -1Vbe as usual. Observe that Q3 current is fixed by QB7.
Title: Re: Opamps - Die pictures
Post by: Zero999 on October 16, 2020, 08:46:21 am
I remember seeing an open loop plot of a certain brand 741 op amp that showed the thermal feedback actually caused the + and - inputs to reverse :o

Of course this would normally be squashed by massive external negative feedback, but still not a good op amp parameter :P

Best,
Sounds very dodgy. No negative feedback won't help, because once the + and - inputs reverse, it becomes positive feedback, which will most likely result in latchup.
Title: Re: Opamps - Die pictures
Post by: capt bullshot on October 16, 2020, 09:56:11 am
Folded cascode would have its bases held at constant voltage and collectors loaded with a mirror rather than a pair of equal, stiff current sources. But it's a similar thing in principle, I think.

Here those "cascode" transistors track voltage across R3 and transfer it to R4. At some high frequency, parallel capacitance across R3 kills those voltage swings to eliminate phase delay through the phase summing circuit from the amplifier's forward path, apparently.

edit
Okay, I will try more clearly. In a classic folded cascode amplifier, Q3 transfers Q1 current swings to a PNP mirror above and phase summing occurs between the output of said mirror and Q4. Here, phase summing occurs between R4 and Q4 and Q4 is just a cascode over that node, while the Q3,Q5 circuit is basically a voltage follower, with +1Vbe offset rather than -1Vbe as usual. Observe that Q3 current is fixed by QB7.

Yes, indeed. It's not the "classic" folded cascode, the circuit just looks somewhat alike. Transferring voltage from R3 to R4 rings some bells (like ideal / diamond transistor), but I don't recognize a known scheme. Could it be an internal current feedback scheme through R4?
Title: Re: Opamps - Die pictures
Post by: magic on October 16, 2020, 10:52:40 am
The point of that is to transfer Q1 current to the Q2 branch of the circuit.

Since Q3 current is constant, it really is not a cascode. Therefore Q1 current has nowhere to go but to R3. This increases/decreases R3 voltage, which is transferred to R4, causing identical increase/decrease in R4 current, which adds to the corresponding opposite change in Q2 current. It's phase summing.

A short way to describe it is that Q3,Q4,Q5 is a resistor-degenerated current mirror biased by two equal collector currents, so in quiescent conditions it simply does nothing besides feeding a current equal to Q5 base current into Q6 base. Then two input stage currents with opposite AC components are fed into the degeneration resistors, resulting in the difference of those currents appearing on Q4 collector.

It's not perfect by the way, because Q4 emitter has nonzero input resistance which to AC currents appears in parallel with R4, so part of the AC current summed at Q4 emitter node escapes through R4 to ground. Depends on the ratio of Q4 intrinsic emitter resistance and R4. R4 can't be too high because if it drops significant voltage, the input transistors will saturate and turn off when their emitters approach ground and likely phase reversal will occur, which this chip is advertised to avoid until some -0.6V. I think the point of this unusual mirror arrangement is to enable operation close to ground and avoid phase reversal below the negative rail.

Current feedback? Dunno. To have feedback, you need to feed something back ;D
What signal is supposed to be fed and from where to where?
Title: Re: Opamps - Die pictures
Post by: magic on October 16, 2020, 11:08:32 am
I remember seeing an open loop plot of a certain brand 741 op amp that showed the thermal feedback actually caused the + and - inputs to reverse :o

Of course this would normally be squashed by massive external negative feedback, but still not a good op amp parameter :P

Best,
Sounds very dodgy. No negative feedback won't help, because once the + and - inputs reverse, it becomes positive feedback, which will most likely result in latchup.
I think it meant that polarity of thermal feedback itself was positive, i.e. the output going one way affected offset voltage in such way that the output went even harder the same way, in absence of normal feedback.
I suppose it shows up as increased open loop gain and perhaps some phase oddity at extremely low frequencies.
Honestly, not sure what's wrong with it.
Title: Re: Opamps - Die pictures
Post by: capt bullshot on October 16, 2020, 12:06:49 pm
The point of that is to transfer Q1 current to the Q2 branch of the circuit.
...
Current feedback? Dunno. To have feedback, you need to feed something back ;D
What signal is supposed to be fed and from where to where?

Read your explanation and studied the schematic - doesn't match.

So, find my fault (or I might be finding it while writing) ;)

If Q1 collector current increases, Q2 collector current is supposed to decrease as their sum is set by QB10.
Increasing Q1 collector current causes R3 voltage to rise.
Decreasing Q2 collector current causes R4 voltage to decrease.
Q3 emitter voltage rising causes its base voltage rising, as Q3 current is constant. Q4 emitter will follow.
Q4 emitter voltage rising increases R4 current, which is opposite to decreasing Q2 collector current.

OK, I've got it now. It's phase summing because these opposite changes add to the desired Q4 collector voltage output. Thanks.

Looks like the output stage (Q10, driven by Q6 through R5) has significant LF voltage gain, too.
Quite a bunch of tricks to achieve single rail operation (input and output range includes "GND"), not that easy to follow.
Title: Re: Opamps - Die pictures
Post by: magic on October 16, 2020, 04:47:50 pm
OK, I've got it now. It's phase summing because these opposite changes add to the desired Q4 collector voltage output.
Sorry for the jargon, I've seen it in the Self amplifier book with an implication that it's a common term in opamp literature.
But frankly, I now can't find any example of it on the Internet, so :-//

Anyway, I did indeed mean adding/subtracting the two opposite phase signals from the differential pair.
Title: Re: Opamps - Die pictures
Post by: Noopy on October 25, 2020, 10:23:50 pm
I had started this High-Power-Opamp-thread: https://www.eevblog.com/forum/projects/opa541-high-power-opamp-die-pictures/ (https://www.eevblog.com/forum/projects/opa541-high-power-opamp-die-pictures/)
Unfortunately there is a OPA541 in the headline and I got some more High-Power-Opamps.  ;D
In future I will post High-Power-Opamps in this thread.



And now welcome the PA-03:


(https://www.richis-lab.de/images/Opamp/18x01.jpg)

+/-75V, 30A, max. 500W power dissipation and 1MHz cutoff frequency! That´s a power device!  8)


(https://www.richis-lab.de/images/Opamp/18x04.jpg)

The PA-03 contains three ceramic carrier (beryllium oxide), a highside powerstage, a lowside powerstage and a circuit to control them.
Apex used a lot of different bondwire diameters.


(https://www.richis-lab.de/images/Opamp/18x05.jpg)

The powerstages were soldered to the package. After that the controlstage was simply glued down. I assume they wanted to protect the controlstage from the heat of the soldering process.


(https://www.richis-lab.de/images/Opamp/18x32.jpg)

It seems there are three different resistor types, a shiny one, a thin rough one and a thick rough one.
Of course they did laser tuning.


(https://www.richis-lab.de/images/Opamp/18x25.jpg)

And there are points to identify the aligment of the masks.


(https://www.richis-lab.de/images/Opamp/18x14.jpg)

Now that doesn´t look quite robust...  ???


(https://www.richis-lab.de/images/Opamp/18x24.jpg)

Apex also had problems with the bonding process...


(https://www.richis-lab.de/images/Opamp/18x08.jpg)

Huuuuuge!  8)
The shunt for overcurrent protection is simply one of the traces leading from a transistor to the output.


(https://www.richis-lab.de/images/Opamp/18x34.jpg)

It´s a Sziklai-Darlington-powerstage.


(https://www.richis-lab.de/images/Opamp/18x15.jpg)

That´s a really good temperature measurement! Datasheet states a response time of 10ms.
You can´t kill the transistors with second breakdown. Second breakdown only is a danger at durations longer than 10ms and there the temperature protection is fast enough.  :box:


(https://www.richis-lab.de/images/Opamp/18x17.jpg)

Input stage is of course a Dual-J-FET for most similar characteristics and a similar temperature.


It´s too late for a longer translation. Please use your favourite translator and take a look at a lot more pictures on my website:

https://www.richis-lab.de/Opamp17.htm (https://www.richis-lab.de/Opamp17.htm)

Of course you can ask me whatever you want here in english.

 :popcorn:
Title: Re: Opamps - Die pictures
Post by: RoGeorge on October 25, 2020, 10:27:34 pm
APEX?!  Like the game?  :D
Title: Re: Opamps - Die pictures
Post by: Noopy on October 25, 2020, 10:28:58 pm
I´m getting old. Didn´t know there is a game with the name APEX.  ;D :-+
Title: Re: Opamps - Die pictures
Post by: T3sl4co1l on October 26, 2020, 01:11:51 am
They had the name before the game existed.  8)

Handle that thing carefully, those are BeO substrates!  Fantastic heat conduction, worth every cent too... ;D

Tim
Title: Re: Opamps - Die pictures
Post by: Noopy on October 26, 2020, 04:16:49 am
Thanks for the hint. It´s not the first BeO-part I have opened. I take care not to cut the ceramic that should be good enough.  :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on November 02, 2020, 10:14:54 pm
(https://www.richis-lab.de/images/Opamp/21x01.jpg)

Let´s look into the famous LM709.


(https://www.richis-lab.de/images/Opamp/21x04.jpg)

That are very small resistor strings! I have never seen such small resistors (with respect to the transistors).


(https://www.richis-lab.de/images/Opamp/21x05.jpg)

The pnp-transistor Q9 shows the normal structure of a pnp-transistor manufactured with a npn-process.
But the pnp-transistor Q13 is different! There is a brown emitter area surrounded by the blue, n+ doping. You can´t see a collector. It seems like Q13 uses the substrate as collector. That´s possible because the collector had to be connected to the negative supply. The buried n+ layer was certainly removed. The n+ base contact frame gives you a quite low resistance leading to the active base area.
It would have been possible to use the isolation diffusion as collector but then the base area would have been too long for a good transistor.


https://www.richis-lab.de/Opamp20.htm (https://www.richis-lab.de/Opamp20.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: David Hess on November 03, 2020, 01:31:55 am
But the pnp-transistor Q13 is different! There is a brown emitter area surrounded by the blue, n+ doping. You can´t see a collector. It seems like Q13 uses the substrate as collector. That´s possible because the collector had to be connected to the negative supply. The buried n+ layer was certainly removed. The n+ base contact frame gives you a quite low resistance leading to the active base area.

That sounds suspiciously like a charge storage PNP.  Widlar himself describes it on page 3 of Linear Technology application note 16:

https://www.analog.com/media/en/technical-documentation/application-notes/an16f.pdf (https://www.analog.com/media/en/technical-documentation/application-notes/an16f.pdf)
Title: Re: Opamps - Die pictures
Post by: Noopy on November 03, 2020, 03:54:39 am
But the pnp-transistor Q13 is different! There is a brown emitter area surrounded by the blue, n+ doping. You can´t see a collector. It seems like Q13 uses the substrate as collector. That´s possible because the collector had to be connected to the negative supply. The buried n+ layer was certainly removed. The n+ base contact frame gives you a quite low resistance leading to the active base area.

That sounds suspiciously like a charge storage PNP.  Widlar himself describes it on page 3 of Linear Technology application note 16:

https://www.analog.com/media/en/technical-documentation/application-notes/an16f.pdf (https://www.analog.com/media/en/technical-documentation/application-notes/an16f.pdf)

Thanks for the hint, that´s very interesting.  :-+

I hope I got it right:
Usually you try to minimize base-emitter-capacitance to get a fast transistor (fast switch-off).
In the charge storage PNP-transistor you try to get a bigger base-emitter-capacitance with fast charges so you can boost a signal through this area. (I suppose switch off is slower.)
In the LM709 output stage that would speed up the lowside getting low. I assume a slower switch off speed is not extremly important because the highside can pull the output upwards.
Title: Re: Opamps - Die pictures
Post by: Noopy on November 05, 2020, 09:00:22 pm
(https://www.richis-lab.de/images/opamp/22x01.jpg)

Mikroelektronika Botevgrad 1УO709 - 1UO709, another 709-opamp.


(https://www.richis-lab.de/images/Opamp/22x02.jpg)

Unfortunately the die was damaged a little.
Nevertheless we can clearly see that it is very similar to the LM709.


https://www.richis-lab.de/Opamp21.htm (https://www.richis-lab.de/Opamp21.htm)


 :popcorn:
Title: Re: Opamps - Die pictures
Post by: Noopy on November 09, 2020, 03:39:34 pm
Let´s take a closer look into a OPA627!  8)

(https://www.richis-lab.de/images/opamp/23x01.jpg)

(https://www.richis-lab.de/images/Opamp/23x02.jpg)

The die is quite big (2,9mm x 2,0mm).


(https://www.richis-lab.de/images/Opamp/23x09.jpg)

The most interesting part is the input stage. There is a matrix of 2x8 transistors forming the two input transistors. Burr-Brown tried to match the metal traces and the silicon traces as good as possible. In the upper left corner there are two green underpasses which are "very" long and wide just to match the underpasses in the lower right corner.

Around the input transistors there are the tuned resistors for input-offset tuning and the current mirror emitter resistors which travel quite a long way to get to the left edge of the die. I assume they wanted to bring some distance between the transistors and the edge of the die and then decided to fill the empty room with the current mirror resistors.

On the right side there are four transistors generating the two cascode transistors of the input stage. The current sink is placed in the center for most equal temperatures.

Above and below the input transistor matrix there are two more input-J-FETs which are connected to two more transistors in the cascode stage.


(https://www.richis-lab.de/images/Opamp/23x08.jpg)

The circuit is a bit different to the schematic in the datasheet. I dont´really understand what is the purpose of the path Q17/Q18-Q6/Q7...  :-// @magic: any ideas?  ;)


More pictures here:
https://www.richis-lab.de/Opamp22.htm (https://www.richis-lab.de/Opamp22.htm)

 :popcorn:
Title: Re: Opamps - Die pictures
Post by: David Hess on November 09, 2020, 04:18:25 pm
The circuit is a bit different to the schematic in the datasheet. I dont´really understand what is the purpose of the path Q17/Q18-Q6/Q7...  :-// @magic: any ideas?  ;)

Could that be transconductance reduction of the input stage?  It is not in the form that I usually see and it is almost always left off of published schematics.
Title: Re: Opamps - Die pictures
Post by: Noopy on November 09, 2020, 06:46:19 pm
Could that be transconductance reduction of the input stage?  It is not in the form that I usually see and it is almost always left off of published schematics.

That's possible.  :-+ ...an interesting way of transconductance reduction. Probably a very clever way for the OPA627.  :-//
Title: Re: Opamps - Die pictures
Post by: magic on November 09, 2020, 08:46:21 pm
If the schematic is to be believed, these are P channel JFETs like in TL071 so you have drawn them upside down. The sources should be "up", the drains should be "down".

Then it looks like Q17,Q18 are simply source followers and Q6,Q7 diodes shift the voltage one Vbe up and drive bases of Q2~Q5. Input stage current is about 8x the current through Q6,Q7 and Q17,Q18, which is set by that current source at the positive rail.

Q8 and Q1 plus something between them (let me guess: a string of diodes or resistor) bootstrap the drains of all those JFETs.

BTW, zeptobars has a higher resolution image.
https://zeptobars.com/en/read/BB-TI-OPA627-opamp-genuine-fake
Title: Re: Opamps - Die pictures
Post by: Noopy on November 10, 2020, 04:25:48 am
Thanks!  :) You are right, the JFETs were rotated. And the numbers were also confusing. I changed that:

(https://www.richis-lab.de/images/opamp/23x08a.jpg)

Is it correct to call J1-J8/Q2-Q3 a cascode?

I didn´t check the parts between Q8 and Q1 but that should be some kind ob voltage drop.  :-+

That´s an interesting input stage! But why did they double the inputs? Why J17/J18 and Q6/Q7?


I know zeptobars had already pictures but I had to take a look into this one because the owner wanted to know whether it´s genuine.  :-/O
Title: Re: Opamps - Die pictures
Post by: magic on November 10, 2020, 10:16:52 am
Not sure. Q6 seems to have ⅛ emitter area of Q2+Q3 and J17 is ⅛ of J1~J8 and the resistors are probably in 8:1 ratio too. These two current paths operate almost identically. The only difference I see so far is that Q6 and J17 current is affected only by Early effect in the current source, but Q2+Q3 and J1~J8 current is affected also by Early effect in Q2+Q3.

Is this difference between J17 and J1~J8 operating current significant? Maybe for THD, or maybe not. Maybe this configuration only plays some role in preventing phase reversal. Maybe they didn't want to do a thermally balanced layout for Q6. Maybe it avoids needing to laser trim R7. Maybe simulation would show something.

BTW, if we connect Q6 emitter to Q2+Q3, we get a configuration analogous to inverted LM101A.
Title: Re: Opamps - Die pictures
Post by: Noopy on November 10, 2020, 12:08:45 pm
Thanks for your interpretation!
A mysterious input stage...  :-/O
Title: Re: Opamps - Die pictures
Post by: David Hess on November 10, 2020, 04:37:47 pm
Is it correct to call J1-J8/Q2-Q3 a cascode?

Yes, I was looking at it completely wrong.  Q2 through Q7 are the cascode transistors for J1 through J8 and J9 through J16.

Quote
That´s an interesting input stage! But why did they double the inputs? Why J17/J18 and Q6/Q7?

J17 and J18 control the base voltage of the cascodes so that they follow the input JFETs making Vds is constant.  The base connection between Q6 and Q8 receives a constant current from the positive supply which creates a constant voltage across R7 and R8.  Q6 and Q7 are connected as diodes so that their Vbe compensates the Vbe of the cascode transistors.

A cascode configuration is common with super-beta input stages because the Vce breakdown voltage is very low, only like 3 to 5 volts.  Sometimes it is used to increase the differential input voltage range by preventing breakdown of base-emitter junction of the input transistors.  I do not know why it would be used with JFETs unless modulation with changing drain voltage was a significant error term, which it could be.  Or maybe these JFETs have a limited maximum Vds?
Title: Re: Opamps - Die pictures
Post by: Noopy on November 10, 2020, 05:20:55 pm
That´s an interesting input stage! But why did they double the inputs? Why J17/J18 and Q6/Q7?

J17 and J18 control the base voltage of the cascodes so that they follow the input JFETs making Vds is constant.  The base connection between Q6 and Q8 receives a constant current from the positive supply which creates a constant voltage across R7 and R8.  Q6 and Q7 are connected as diodes so that their Vbe compensates the Vbe of the cascode transistors.

A cascode configuration is common with super-beta input stages because the Vce breakdown voltage is very low, only like 3 to 5 volts.  Sometimes it is used to increase the differential input voltage range by preventing breakdown of base-emitter junction of the input transistors.  I do not know why it would be used with JFETs unless modulation with changing drain voltage was a significant error term, which it could be.  Or maybe these JFETs have a limited maximum Vds?

That is convincing, thanks!  :-+
Title: Re: Opamps - Die pictures
Post by: David Hess on November 10, 2020, 05:33:32 pm
I wonder what advantages this topology would have in a discrete design, with JFET (or bipolar) followers driving common-base bipolars to make a differential input stage.  Noise will be higher.

Incidentally, some people object to calling it a cascode and consider it a cascade (?) when it is the emitter or source of the input transistor driving the emitter or source of a cascode transistor and the transconductance is controlled by the emitter and source resistances plus any added resistance as in this case.

If you squint a little, then it is a differential pair made up of complementary transistors and in this case, completely different types of transistors.  I have run across this complementary differential pair before in high frequency and high frequency high voltage circuits.
Title: Re: Opamps - Die pictures
Post by: Kleinstein on November 10, 2020, 06:02:08 pm
Keeping the DS voltage of the input JFETs about constant also helps getting a constant and reduced input capacitance. With conventional JFET OPs the bootstrapping may extend to not just the drain voltage, but also to the isolation from the substrate.  AFAIK the OPA627 is a kind of SOI device and does not use the conventional junction isolation, so it would not need this extra step.

One weakness of JFET amplifier is a voltage dependent input capacitance that can create THD.
Title: Re: Opamps - Die pictures
Post by: magic on November 10, 2020, 06:15:55 pm
Indeed, high source impedance and variable input capacitance form a variable RC lowpass which (slightly) attenuates positive and negative half-cycles by different amount and distorts the waveform.

OPA6x7 are clearly advertised as dielectric-isolated ICs and have long been known as good performers in this regard. More recently, TI claims that OPA140/OPA1641 offer similar performance. Perhaps they came up with some cheaper SOI process.

Bipolar opamps have similar problems with high source impedance. Their BC capacitance isn't constant and neither are base currents.
Title: Re: Opamps - Die pictures
Post by: Noopy on November 10, 2020, 07:31:35 pm
Incidentally, some people object to calling it a cascode and consider it a cascade (?) when it is the emitter or source of the input transistor driving the emitter or source of a cascode transistor and the transconductance is controlled by the emitter and source resistances plus any added resistance as in this case.

Just to be clear (after taking one more closer look):
J1-J18 and Q2-Q7 don´t form a cascode but a cascade.
The whole circuit has a similar effect: It hold´s the DS voltage of the input transistors constant but it´s no cascode.

Does everybody agree with me?  :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on November 13, 2020, 01:08:10 pm
I have taken pictures of the side of the OPA627-die:


(https://richis-lab.de/images/Opamp/23x10.jpg)

I pretty sure the gap directly under the surface is the dielectrical isolation.  :-/O


(https://richis-lab.de/images/Opamp/23x11.jpg)

Here another OPA627-die. The upper die is ~20µm thick. The whole stack is 250µm high.

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on November 13, 2020, 02:17:42 pm
Old SOI processes were pretty crude, involving the following steps:

- etching deep trenches on the top side and filling them with silicon oxide
- covering the whole top surface in silicon oxide
- growing hundreds µm of polycrystalline silicon or thermally fusing another wafer on top
- flipping everything upside down
- precisely grinding away almost all of the original wafer until the isolation trenches are exposed

This die looks like it may have been produced that way. I think it's a big part of why those old BB chips are still one of the most pricey opamps around.
Title: Re: Opamps - Die pictures
Post by: Noopy on November 13, 2020, 03:02:54 pm
Old SOI processes were pretty crude, involving the following steps:

- etching deep trenches on the top side and filling them with silicon oxide
- covering the whole top surface in silicon oxide
- growing hundreds µm of polycrystalline silicon or thermally fusing another wafer on top
- flipping everything upside down
- precisely grinding away almost all of the original wafer until the isolation trenches are exposed

This die looks like it may have been produced that way. I think it's a big part of why those old BB chips are still one of the most pricey opamps around.

Very interesting! Thanks for the Explanation!  :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on November 15, 2020, 05:30:09 am
Here some older pitctures of a LM741:

(https://www.richis-lab.de/images/Opamp/24x01.jpg)

(https://www.richis-lab.de/images/Opamp/24x03.jpg)

https://www.richis-lab.de/Opamp23.htm (https://www.richis-lab.de/Opamp23.htm)

I already had uploaded the pictures in my Gould 4074 teardown but I need the chapter for the next opamp...  :-/O ;)
Title: Re: Opamps - Die pictures
Post by: Noopy on November 16, 2020, 12:25:22 pm
(https://www.richis-lab.de/images/Opamp/25x01.jpg)

The "next opamp" is a LH0042, a J-FET-input Hybrid-Opamp.


(https://www.richis-lab.de/images/Opamp/25x02.jpg)

The LH0042 is built with two dies (J-FET-input and the rest of the opamp) on a ceramic substrate.


(https://www.richis-lab.de/images/Opamp/25x05a.jpg)

On the small die there are two J-FETs apparently built by National Semiconductor.


(https://www.richis-lab.de/images/Opamp/25x04.jpg)

The second die is a modified LM741-die.


(https://www.richis-lab.de/images/Opamp/25x06.jpg)

Here you can see the differences.
The actual circuit around Q8 is a little different to the LM741-schematic (no current mirror) but in the LH0042 it is missing completely. The J-FET-die is placed on an area of the positive supply.
The input transistors Q1/Q2 are missing so that the J-FETs can control the cascade transistors Q3/Q4.


https://www.richis-lab.de/Opamp24.htm (https://www.richis-lab.de/Opamp24.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on November 16, 2020, 05:52:42 pm
That's fishy, 741 circuit can't work correctly without the Q8/Q9 mirror, it's critical for regulating input stage current.
It looks like they included additional small collectors on Q3/Q4 and connected them to the base, like in LM101A. Then the input stage is fine.
And it seems they cheated and did the same thing on LM741 too.

edit
Perhaps the rest of the circuit is LM101A too. You could try LM107 - an LM101A with internal compensation. It may be the same silicon, with Q1/Q2 connected normally but Q8 disconnected and bypassed.
Title: Re: Opamps - Die pictures
Post by: Noopy on November 16, 2020, 06:10:01 pm
You are right there are two collectors on Q3 and Q4 and one of each is connected to their common base. (in the LH0042 and in the LM741)

You can find that circuit in the schematic of the LM148 which provides four LM741:

(https://richis-lab.de/images/Opamp/25x09.jpg)


Can you explain to me why exactly the Q8/Q9 is neccesary? At first sight I would say a constant current through the base of Q3/Q4 gives a constant current sum in the differential amplifier so everything is ok?  :-// But the base-collector connection will prevent saturation of Q3/Q4, right?


BTW: NS has printed three different schematics for the LM741 (LM741, LH0042 and LM148). In every schematic the circuit is a little bit different (ignoring the J-FET input in the LH0042).
Title: Re: Opamps - Die pictures
Post by: magic on November 16, 2020, 07:03:38 pm
Maybe it could work, but Q10 current would need to be reduced by beta of Q3/Q4. And then input stage current would depend on beta of Q3/Q4, which is subject to random production variation and thermal drift. Actually, I think the original 101 may have worked that way but later the 741 and 101A types used more complex biasing to improve input stage regulation.
Title: Re: Opamps - Die pictures
Post by: David Hess on November 16, 2020, 07:07:56 pm
You are right there are two collectors on Q3 and Q4 and one of each is connected to their common base. (in the LH0042 and in the LM741)

That configuration is used by the LM301A as part of the improvement over the LM301 to control input bias current.  Wouldn't National have used their own chip instead of Fairchild's?

Quote
You can find that circuit in the schematic of the LM148 which provides four LM741

The 5 picofarad compensation capacitance indicates that input stage transconductance was reduced which might be backed up by lower input bias current.  I wonder if the LM148 schematic is complete since Q8 should not be needed; see below.

Quote
Can you explain to me why exactly the Q8/Q9 is necessary? At first sight I would say a constant current through the base of Q3/Q4 gives a constant current sum in the differential amplifier so everything is ok?  :-// But the base-collector connection will prevent saturation of Q3/Q4, right?

Q8 and Q9 make the current pulled out of the bases of Q3 and Q4 constant so the input bias current is constant over the input common mode range.  As the input common mode voltage rises, in bias current rises, increasing current through Q8 and Q9, so less current is provided by the base connections to Q3 and Q4, and input bias current is restored.

Contrast that with the LM301 which lacked that circuit and had a wider range of input bias current, which was improved in the LM301A.

If anybody has a copy of Widlar's paper on the LM301A, I would like to see it.  All I find are references to its existence - Robert J. Widlar, “IC Op Amp with Improved Input-Current Characteristics,” IEEE, December 1968.
Title: Re: Opamps - Die pictures
Post by: magic on November 18, 2020, 11:02:33 am
Actually I was wrong: input stage current of the original LM101 was not that completely uncontrolled. Base current of Q3/Q4 was generated by mirroring base current of another (presumably similar) PNP, whose collector current was regulated, albeit poorly so and with negative thermal coefficient.

I don't think Widlar's paper exists anywhere on the Internet, but plausible explanations of LM101, LM741 and LM101A circuitry are found here:
http://www.ee.bgu.ac.il/~angcirc/History/Solutions_2003_2004_B/SomeStuff/History18opamp.pdf (http://www.ee.bgu.ac.il/~angcirc/History/Solutions_2003_2004_B/SomeStuff/History18opamp.pdf)
Title: Re: Opamps - Die pictures
Post by: djerickson on November 19, 2020, 01:34:01 am
I'd like to see a photo of LT1013. Precision dual, single supply, multi-sourced, and low cost. Almost a perfect part, BUT.... The SOIC pinout is not standard, I assume because the die had to be rotated to fit the SOIC8 package. So instead I pay lots more for OP279s.   So sad:(
Dave
Title: Re: Opamps - Die pictures
Post by: Noopy on November 19, 2020, 04:12:00 am
I'd like to see a photo of LT1013. Precision dual, single supply, multi-sourced, and low cost. Almost a perfect part, BUT.... The SOIC pinout is not standard, I assume because the die had to be rotated to fit the SOIC8 package. So instead I pay lots more for OP279s.   So sad:(
Dave

I will look for one.  :-+
Title: Re: Opamps - Die pictures
Post by: David Hess on November 20, 2020, 12:43:40 am
I'd like to see a photo of LT1013. Precision dual, single supply, multi-sourced, and low cost. Almost a perfect part, BUT.... The SOIC pinout is not standard, I assume because the die had to be rotated to fit the SOIC8 package. So instead I pay lots more for OP279s.

The LT1013 was not the only older dual part to suffer from that problem in the SOIC package.  Linear Technology later released newer parts with similar performance and smaller dies but as you note, the LT1013 is the one with multiple sources making it the low cost choice.
Title: Re: Opamps - Die pictures
Post by: Noopy on November 21, 2020, 02:06:48 pm
I'd like to see a photo of LT1013. Precision dual, single supply, multi-sourced, and low cost. Almost a perfect part, BUT.... The SOIC pinout is not standard, I assume because the die had to be rotated to fit the SOIC8 package. So instead I pay lots more for OP279s.   So sad:(
Dave
I will look for one.  :-+

I have the LT1013 in the line. Next decap session I will put it into the ofen.  :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on December 12, 2020, 08:47:36 pm
(The LT1013 will come soon!)


(https://www.richis-lab.de/images/opamp/26x01.jpg)

Today I have a КP597CA1 (KR597SA1) for you, a soviet AM685 clone.
The brown package isn´t lightproof. That can be a problem if you want to compare values with small differences and the light is fluctuating...  >:D


(https://www.richis-lab.de/images/Opamp/26x04.jpg)

The brown material isn´t easy to remove...


(https://www.richis-lab.de/images/Opamp/26x06.jpg)

...but the picture is good enough to identify every component.


More pictures here:

https://www.richis-lab.de/Opamp25.htm (https://www.richis-lab.de/Opamp25.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on December 22, 2020, 09:52:21 pm
I'd like to see a photo of LT1013.


Done that:


(https://www.richis-lab.de/images/opamp/27x01.jpg)

(https://www.richis-lab.de/images/Opamp/27x03.jpg)

There is some silicone potting on the die.


(https://www.richis-lab.de/images/Opamp/27x02.jpg)

A different part and the die is still in the package.


(https://www.richis-lab.de/images/Opamp/27x05.jpg)

The die is 2,4mm x 1,9mm.


(https://www.richis-lab.de/images/opamp/27x08.jpg)

The design dates back to 1987, manufactured in 2000.


(https://www.richis-lab.de/images/Opamp/27x04.jpg)

The pink part makes it possible to got down to 0V (with single supply).
Datasheet explains that with other opamps negative voltages on one input of such an input stage can lead to a phase reversal. In my view phase reversal is not really the right naming. With negative voltages the differential amplifier (dark green) can be driven into saturation and so the whole circuit is buggy. The output goes high but that´s not really a phase reversal. In the LT1013 the transistors Q21/Q22/Q27/Q28 supply current to the input stage as soon as the voltage is low enough so there is no saturation problem in the following stage.
There is a small mistake in the datasheet schematic. Q28 is connected to the positive supply.
I´m not perfectly sure what the grey part does. In my view you need these components if you drive the differential stage to hard. The next stage can only source current so too much current has to be drained over Q29/Q8. Q9/Q11/Q12/Q13 compensates the current in the left leg.
The VAS (and it´s drivers Q10/Q18) is cyan.
Steering of lowside-output-transistor Q34 is realized by the yellow part. Quite interesting constellation.
The right blue part generates reference voltages. There are a lot of current mirrors generating the currents for the different stages.
The green part is an overcurrent protection.


(https://www.richis-lab.de/images/Opamp/27x11.jpg)

Most of the parts can be identified on the die.
Interesting that there is a second V+ bondpad...  :-//


(https://www.richis-lab.de/images/Opamp/27x07.jpg)

The input stage is quite symmetrical and partly cross wired.
The input resistors are placed in parallel too.


(https://www.richis-lab.de/images/Opamp/27x09.jpg)

That´s interesting. The emitter resistors of the current sources of the input stage can be adjusted (offset adjust).
There are two long resistors. In the red path you can switch in a 2R, a R, a R/2 and a R/4 resistor giving you 16 steps of adjustment. In addition in the green path there is a 4R resistor for inverting the adjustment.
But wait! There are five fuses but only three testpads and one bondpad!  ??? It seems like they found a way to cut only one fuse although there are two in series.


(https://www.richis-lab.de/images/opamp/27x10.jpg)

It seems like the metal layer on the green resistors makes it possible to do some bigger adjustment if necessary.


(https://www.richis-lab.de/images/Opamp/27x14.jpg)

I used my very special simulation tool MS Powerpoint to show the thermal gradients.  ;D
Well you can imagine that the placement of the input transistors is optimized so they see very little temperature difference which gives you low offset drift.


(https://www.richis-lab.de/images/Opamp/27x13.jpg)

Also very interesting are the capacitors. The 21pF- and the 2,5pF-capacitor are obvious and built like we now integrated capacitors.
But there are a lot of other capacitors which need a lot more area. Thankfully these capacitors are reffered to ground. To reduce the necessary silicon area the capacitors are integrated under the active areas. You can see a green frame, that´s the capacitor.


(https://www.richis-lab.de/images/Opamp/27x15.jpg)

In the lower right corner there is a metal-fuse and a testpad which doesn´t interact with the circuit. I assume that´s a kind of binning...  :-//


More pictures here:

https://www.richis-lab.de/Opamp26.htm (https://www.richis-lab.de/Opamp26.htm)

 8)
Title: Re: Opamps - Die pictures
Post by: David Hess on December 23, 2020, 05:16:38 am
There is some silicone potting on the die.

Analog ICs require a compliant encapsulation inside of a plastic package to prevent strain on the die from ruining precision.

I remember hearing a story that the managers at National kept asking why linear IC packaging had to cost more and why couldn't they use the cheaper packaging for digital ICs.  Then a management genius shifted packaging to the digital IC group without telling the engineers and a couple months later all of their linear ICs started failing testing, so they were without analog ICs to sell for several months and ended up buying analog ICs where possible from competitors to fulfill orders.
Title: Re: Opamps - Die pictures
Post by: magic on December 23, 2020, 09:02:15 am
I´m not perfectly sure what the grey part does.
My guess: Q13,Q14 generate equal current as Q16 and Q11 base current mirrored by Q12 into Q7 collector makes up for Q7,Q8 base current. Q12 also maintains Q11 Vce at similar level as Q7,Q8. Ideally Q11 would have equal area as Q7+Q8, it seems they didn't bother.
Similarly, Q9 base connected to Q7 collector balances Q10 base current drawn by Q8 collector. This trick is present in LM358, even if not shown on most schematics.
Title: Re: Opamps - Die pictures
Post by: Noopy on December 23, 2020, 09:57:18 am
As always I´m glad for your input, magic.  :-+
Let me check your points one by one:

Q13,Q14 generate equal current as Q16 and Q11 base current mirrored by Q12 into Q7 collector makes up for Q7,Q8 base current.
Sounds quite reasonable.  :-+
But how can you be sure that the current through Q11/Q9 (which is mirrored into base of Q7/Q8) is equal to the base current of Q7/Q8?


Q12 also maintains Q11 Vce at similar level as Q7,Q8.
But Vce of Q7 is Vbe of Q7, isn´t it?
Vce of Q11 is Q11_Vbe + Q12_Vbe.  :-//


Similarly, Q9 base connected to Q7 collector balances Q10 base current drawn by Q8 collector. This trick is present in LM358, even if not shown on most schematics.
You wanted to write "Q29 base connected to Q8 collector...", didn´t you?
Current flowing from "outside" (Q10) into the right leg of the differential amplifier is steering Q29 which gives us more current in the left leg of the current mirror. That gives us more current in the right leg, where the current out of Q10 is compensated and because of that nobody in the upper part of the differential amplifier is bothered by Q10. Is that correct?
Title: Re: Opamps - Die pictures
Post by: exe on December 23, 2020, 12:29:57 pm
all of their linear ICs started failing testing, so they were without analog ICs to sell for several months and ended up buying analog ICs where possible from competitors to fulfill orders.

I heard this story too and I wonder how realistic it is. How likely that parts from competitors meet same specs like noise, bias, drift, and other parameters?
Title: Re: Opamps - Die pictures
Post by: daqq on December 23, 2020, 12:41:34 pm
Quote
How likely that parts from competitors meet same specs like noise, bias, drift, and other parameters?
Depending on the product could easily be true. The OP07 op amp is made by Ti and Analog currently, at the time was likely made by more. Pretty much everyone makes the venerable 741 or other jellybean op amps. The LM399 is made by both Analog and some time ago was made by National Instruments as well. Also a compatible part was made by Tesla (Czechoslovakia), MAB399.

There may be some minor differences, but they should be drop in replacements.
Title: Re: Opamps - Die pictures
Post by: magic on December 23, 2020, 03:45:36 pm
I have done some quick and dirty testing of voltage noise in a few opamps (including 553x, 4558, and yes, OP07) and TI tends to have a bit more 10Hz noise than competitors like Analog, vintage Philips, JRC, whichever applicable.
Nothing out of spec, but if you expect parts better than 1970's specs, prepare for |O
TI has some impressive low noise parts on modern processes, but their jellybeans simply didn't look that great in my tests. Observe that they rarely publish typical noise spectrum plots for those parts.

how can you be sure that the current through Q11/Q9 (which is mirrored into base of Q7/Q8) is equal to the base current of Q7/Q8?
Only base current of Q11 is mirrored, and collector current of Q11 appears equal to the total current through Q7 and Q8.

Similarly, Q9 base connected to Q7 collector balances Q10 base current drawn by Q8 collector. This trick is present in LM358, even if not shown on most schematics.
You wanted to write "Q29 base connected to Q8 collector...", didn´t you?
Current flowing from "outside" (Q10) into the right leg of the differential amplifier is steering Q29 which gives us more current in the left leg of the current mirror. That gives us more current in the right leg, where the current out of Q10 is compensated and because of that nobody in the upper part of the differential amplifier is bothered by Q10. Is that correct?
I think Q9 balances Q10 like in LM358 (caution: different numbering below).
(https://www.eevblog.com/forum/projects/whats-inside-the-cheapest-and-fakest-jellybean-opamps/?action=dlattach;attach=946606;image)

I'm not sure what exactly Q29 is trying to achieve, but it only feeds some base current into Q7,Q8 so its own base current should be comparatively lower.
Title: Re: Opamps - Die pictures
Post by: exe on December 23, 2020, 03:55:34 pm
TI has some impressive low noise parts on modern processes, but their jellybeans simply didn't look that great in my tests. Observe that they rarely publish typical noise spectrum plots for those parts.

That's what I heard on multiple occasions, presumably due to die shrinkage (smaller transistors == more noise, afaik). Still, please post some data and how you measured it if you have them. That's because most people who make such claims don't provide details, and I'm a bit suspicious for claims without data, esp. when people talk about audio amplifiers. So much audiopholery around :(.
Title: Re: Opamps - Die pictures
Post by: Noopy on December 23, 2020, 09:13:51 pm
I think now I'm on the right track:
- Q29 is necessary to transfer the base potential of Q10 to Q9.
- Q9 removes the Vbe of Q29.
- Q11 acts like Q10 because
   - it conducts the same current (current sources Q13 and Q14),
   - Q11 (NPN) emitter potential is the same as Q10 (PNP) base potential
- Base current of Q11 will be similar to base current of Q10. Q12 just has to mirror this current into the left leg of the differential amplifier to compensate Q10.
Title: Re: Opamps - Die pictures
Post by: magic on December 23, 2020, 11:42:21 pm
That's what I heard on multiple occasions, presumably due to die shrinkage (smaller transistors == more noise, afaik). Still, please post some data and how you measured it if you have them. That's because most people who make such claims don't provide details, and I'm a bit suspicious for claims without data, esp. when people talk about audio amplifiers. So much audiopholery around :(.
Well, quick and dirty, as I said ;)
I set it for 60dB or 80dB gain using low value resistors (1 ohm is OK for the lower resistor) and fed the output to a soundcard for recording and spectral analysis with software (RMAA will do).
Caveats / tradeoffs:
- too high feedback resistance and Johnson noise may become non-negligible
- too low feedback resistance and the chip may fail to drive it
- GBW limit causes gradual roll-off at higher audio band
- watch out for output at the rail when the chip's offset voltage is too high
- put 50~100R in series with the output or it may oscillate
- I recommend soldering a board because parasitic resistance of breadboards may measurably add to low value resistors

You may not know the exact sensitivity of the soundcard and its frequency response at the low end, but even then comparisons can be made at least. I don't remember the details, but perhaps a few dB difference at the edge of my soundcard's bandwidth (10Hz) and little difference at 100Hz and above for TI. I also got my hands on some very old NE5534 from Philips and they were a fair bit worse than later production, including TI. From China, but for a variety of reasons I'm >90% confident they were legit :D

Potential improvements under consideration for future attempts:
- lower DUT gain to increase bandwidth, add a low noise post-amp to overcome the soundcard's 1/f noise (NE5534, LM4562, ADA797, LT1028, that sort of stuff)
- calibrate the soundcard's response with a precision white noise generator, this could perhaps be a ~100k resistor amplified by low flicker noise JFET opamp (OPA1641/140 looks promising)
Title: Re: Opamps - Die pictures
Post by: David Hess on December 24, 2020, 12:14:36 am
all of their linear ICs started failing testing, so they were without analog ICs to sell for several months and ended up buying analog ICs where possible from competitors to fulfill orders.

I heard this story too and I wonder how realistic it is. How likely that parts from competitors meet same specs like noise, bias, drift, and other parameters?

It is very likely when they are alternate sources for the same parts.
Title: Re: Opamps - Die pictures
Post by: exe on December 24, 2020, 08:49:34 am
Well, quick and dirty, as I said ;)

Thanks for sharing details. Did you use shielding? I've built an LNA from single ad8428 (fixed gain 2000 or ~66db), and in my environment it very easily saturates. I'm still yet to learn how to use it. I bought a metal candy box for shielding, only inside the box it is possible to do something with it, otherwise I see a square wave from rail to rail.
Title: Re: Opamps - Die pictures
Post by: magic on December 24, 2020, 01:20:15 pm
No shielding, just assembled it on my desk, gave it a floating linear PSU and ignored the spikes at multiplies of 50Hz ;)
Despite high gain, this circuit is not very susceptible to noise thanks to low impedances everywhere.
As usual, minimize the traces on IN-, connect the gain resistor to ground close to IN+, take the output ground from there.
Title: Re: Opamps - Die pictures
Post by: Noopy on January 12, 2021, 02:09:06 pm
(https://www.richis-lab.de/images/Opamp/28x01.jpg)

Today I have a Apex PA240 for you: +/-175V, 60mA, 120mApeak, 3MHz, 30V/µs.


(https://www.richis-lab.de/images/Opamp/28x02.jpg)

In the datasheet there is a simplified schematic. ...it looks like they have painted the transisors one by one in powerpoint or a similar special tool...  :o ;D


(https://www.richis-lab.de/images/Opamp/28x10.jpg)

(https://www.richis-lab.de/images/Opamp/28x03.jpg)

Unfortunately the die is coated with some pretty tough varnish. Decapping results in some minor damage.  :-[
The PA240 uses two metal layers and some pretty special looking transistors.


(https://www.richis-lab.de/images/Opamp/28x04.jpg)

The design was developed in 2004 and today it´s already obsolete...  :--


(https://www.richis-lab.de/images/Opamp/28x05.jpg)

Here you can see the input stage.


(https://www.richis-lab.de/images/Opamp/28x06.jpg)

The two input signals are routed close to each other and are shielded with the negative supply potential.
In the input lines there are 2*6 resistors. The resistors look like they were tuned. On top of the left resistors there is a short circuit which is absent on top of the right resistors.


(https://www.richis-lab.de/images/Opamp/28x08.jpg)

The input transistors are quite big. The source resistors are split in eight resistors which are connected crossways for low temperature drift.
In the lower right and left corners there are the four input protection zener diodes.


(https://www.richis-lab.de/images/Opamp/28x09.jpg)

Above the input transistors there are four crisscross connected transistors which do the current mirroring.
And we see again crisscross wired source resistors.


(https://www.richis-lab.de/images/Opamp/28x11.jpg)

In the output stage the highside and the lowside each uses three big transistors.


(https://www.richis-lab.de/images/Opamp/28x07.jpg)

The power transistors look similar to the "normale, discrete" power MOSFETs.


https://www.richis-lab.de/Opamp27.htm (https://www.richis-lab.de/Opamp27.htm)


 :-/O
Title: Re: Opamps - Die pictures
Post by: exe on January 12, 2021, 05:09:53 pm
 I'm surprised how leads are close to each other for such a high-voltage device (350V max total power supply).
Title: Re: Opamps - Die pictures
Post by: Noopy on January 12, 2021, 05:33:48 pm
Datasheet states:
"High  voltage  considerations  should  be  taken  when  designing  board  layouts  for  the  PA240.  The  PA240  may  require  a derate  in  supply  voltage  depending  on  the  spacing  used  for board  layout."
350V is possible but it's quite tight.
Title: Re: Opamps - Die pictures
Post by: magic on January 12, 2021, 05:41:27 pm
Are you really sure that all matched transistors are cross-quads except for the input pair? That seems rather weird :-//
Title: Re: Opamps - Die pictures
Post by: Noopy on January 12, 2021, 05:46:54 pm
Are you really sure that all matched transistors are cross-quads except for the input pair? That seems rather weird :-//

Well the picture quality isn't perfect but I'm pretty sure the input transistors are only two...  :-//
Title: Re: Opamps - Die pictures
Post by: Noopy on January 21, 2021, 08:18:34 pm
Today I have a comparator, a LM306, for you:

(https://www.richis-lab.de/images/Opamp/09x01.jpg)

(https://www.richis-lab.de/images/Opamp/09x02.jpg)

(https://www.richis-lab.de/images/Opamp/09x04.jpg)


https://www.richis-lab.de/Opamp09.htm (https://www.richis-lab.de/Opamp09.htm)


It´s a comparator, not a normal opamp. Note the difference.  :-/O :)


UPDATE


(https://www.richis-lab.de/images/Opamp/09x05.jpg)

I have identified the parts on the die. Thank god the LM306 is not too complex.


(https://www.richis-lab.de/images/Opamp/09x07.jpg)

(https://www.richis-lab.de/images/Opamp/09x06.jpg)

The manufacturing process is "quite simple". You have a p-doped substrate. On top of the substrate you apply the heavily n-doped collector connector (first brown mask). Then you apply a uniform n-doped layer over the surface. To isolate the components a heavily p-doped fence structure is organized with the second, dark green mask. On top of the collector connector the base area get´s p-doped (light green mask). The red mask gives you a strong n-doping to form the emitter and the connection to the collector connector. Finally vias are etched with one mask and metal layer is formed with the last mask.
You can find some blur in the via mask. Perhaps that is the beginning of corrosion. Eventually the protective silicone oxide on top of the die is removed and there is no metal layer closing the hole.


(https://www.richis-lab.de/images/Opamp/09x08.jpg)

While the small transistors can withstand 15V the big one at the output is specified with 24V. To achieve the higher breakdown voltage there is a wide frame built with the base material around the transistor. The lower doping gives you a higher breakdown voltage.  :-+


(https://www.richis-lab.de/images/Opamp/09x10.jpg)

After seven month in a "normal" enviroment (15-25°C, <60% r.H.) the die shows quite a lot of corossion.  :o
Perhaps the silicon oxide protection layer is damaged after all these years (like seen in the MAA723: https://www.richis-lab.de/LM723_04.htm (https://www.richis-lab.de/LM723_04.htm)).


(https://www.richis-lab.de/images/Opamp/09x12.jpg)

Lights on!  8)


(https://www.richis-lab.de/images/Opamp/09x13.gif)

(https://www.richis-lab.de/images/Opamp/09x14.jpg)

With a slow rectangle signal at the input you can see the LM306 circuit changing the current pathes. (top=>down: D1, D2, D3)
Video: https://www.richis-lab.de/images/Opamp/09x13.mp4 (https://www.richis-lab.de/images/Opamp/09x13.mp4)
You can see that the output transistor is never switched off completely


https://www.richis-lab.de/Opamp09.htm (https://www.richis-lab.de/Opamp09.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on January 21, 2021, 08:51:36 pm
After seven month in a "normal" enviroment (15-25°C, <60% r.H.) the die shows quite a lot of corossion.  :o
Do you mean those small spots?
Are you sure it's not just dust?

My dice catch similar crud after a few months of storage, but a wipe with IPA soaked cloth takes care of that.
Title: Re: Opamps - Die pictures
Post by: Noopy on January 21, 2021, 09:02:31 pm
After seven month in a "normal" enviroment (15-25°C, <60% r.H.) the die shows quite a lot of corossion.  :o
Do you mean those small spots?
Are you sure it's not just dust?

My dice catch similar crud after a few months of storage, but a wipe with IPA soaked cloth takes care of that.

No, that is not dust. I'm sure with that. I have seen enough dust.  :D
I'm pretty sure that is something on the surface but in the silicon.
In the green areas the spots are brown. That has to be something like corrosion in the silicon.
Title: Re: Opamps - Die pictures
Post by: exe on January 22, 2021, 07:10:12 pm
That has to be something like corrosion in the silicon.

My best guess is it's something to do with manufacturing. Like, reagents were not properly washed (I assume the can was hermetically sealed).
Title: Re: Opamps - Die pictures
Post by: Noopy on January 22, 2021, 07:13:18 pm
Just to clarify: After opening the package the die was perfectly "clean" as you can see in the pictures. The dots came after 7 month in normal atmosphere.
Title: Re: Opamps - Die pictures
Post by: Noopy on February 08, 2021, 01:55:07 pm
(https://www.richis-lab.de/images/opamp/29x01.jpg)

Toshiba TA75558 dual-opamp


(https://www.richis-lab.de/images/opamp/29x02.jpg)

The circuit is quite common.
There is a small mistake. Around the bias circuit for the output stage there are two connection dots missing (one the right side, on the left side the mistake is corrected).
I´m not perfectly sure about D1. What exactly is the purpose of this diode? A DC-path to the output? In theory without external circuitry the output level is undefined. :-// (@magic?  ;))


(https://www.richis-lab.de/images/opamp/29x03.jpg)

The die is 1,4mm x 1,2mm and quite symmetrical.


(https://www.richis-lab.de/images/opamp/29x07.jpg)#

Identifying the parts is no bigger problem.
In the input stage there are round pnp-transistors.
They used pinch resistors to save silicon area. It´s interesting they didn´t use a pinch resistor for R1 therefore it got very long.
C1 refers to the negative supply and because of that just needed a green area against the substrate. In contrast C2 uses the green layer and the metal layer.


(https://www.richis-lab.de/images/opamp/29x10.jpg)

D2 is integrated on both sides of the die but got connected only on the right side.


(https://www.richis-lab.de/images/opamp/29x11.jpg)

Q15 and D2 are not really easy to spot.
The J-FET Q15 seems to consist of an area that is connected to Vcc and the bias circuit in the upper right corner. On top of this area there is a layer connected to Vee. The lower layer is probably n-doped and the upper layer is p-doped so you get the J-FET you need.
There is a reddish stripe going into the Vee-area. That´s probably the highly n-doped emitter material which gives you a zener to Vee.


(https://www.richis-lab.de/images/opamp/29x09.jpg)

Q10, D1 and C2 are also interesting parts.
Q10 collector potential is the same as the potential of the lower C2 electrode. Because of that Q10 has no own collector contact but is integrated in the surrounding n-doped area of C2. Since the lower electrode of C2 is highly n-doped and there is a buried highly n-doped layer under all the parts there is a low impedance connection between Q10 collector and the lower potential of C2.
D1 is connected in parallel to C2. Because of that D1 is constructed by integrating a small p-doped area in the n-doped area around C2 and connecting it to the upper metal electrode of C2. You can see the outlines of the contact and the p-doped area in the metal layer.


(https://www.richis-lab.de/images/opamp/29x08.jpg)

The output stage contains two big transistors with one dual emitter resistor and the output resistor leading to the output bondpad.
The output stage bias circuit is integrated in a small area that acts as a collector for both transistors.


Some more pictures:

https://www.richis-lab.de/Opamp28.htm (https://www.richis-lab.de/Opamp28.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: exe on February 08, 2021, 02:02:56 pm
I'm surprised how many (cheap) opamps use jfets inside. My understanding is, they are very unpredictable. At least discrete ones. So, does it mean jfets inside ICs have tighter tolerances, or circuits simply don't care if there is a, say, 5x variation to Idss?
Title: Re: Opamps - Die pictures
Post by: Noopy on February 08, 2021, 02:07:34 pm
Often these J-FETs just have to act as cheap current sources.
In my "glowing-LM723-pictures" we have seen that such a J-FET current is changing quite heavily with voltage. But it´s ok to get a bias reference out of a zener.
Title: Re: Opamps - Die pictures
Post by: Noopy on February 08, 2021, 03:16:13 pm
I´m not perfectly sure about D1. What exactly is the purpose of this diode? A DC-path to the output? In theory without external circuitry the output level is undefined. :-// (@magic?  ;))

Aha! D1 prevents saturation of Q6 and Q10 of course!  |O ;D
Title: Re: Opamps - Die pictures
Post by: magic on February 08, 2021, 07:33:59 pm
Of course.
BTW, you swapped Q2 and Q3 on the annotated die image ;)
Input stage layout looks a bit lame, it seems needlessly sensitive to thermal gradients generated by the output stage. RC4558 (which this chip is probably equivalent to) has the input transistors horizontally; see zeptobars.

The N-JFETs widely used for biasing are so-called "epi-FETs" and they are quite terrible: poor tolerance and their gate can only be ground. They typically drive shunt references (here: D2) or similar things so none of it matters.

The P-JFETs used in TL072/LF155/etc require some additional processing IIRC and offer TL072/LF155-level performance, by definition ;)
One trick that TL072 uses to improve JFET matching is the "common centroid" input stage arrangement also used in precision bipolar opamps.

Some CMOS opamps take it even further, the LMC6001 has 16 input transistors in two sets of 8; also on zeptobars.
Title: Re: Opamps - Die pictures
Post by: Noopy on February 09, 2021, 04:27:48 am
BTW, you swapped Q2 and Q3 on the annotated die image ;)

Thanks! I have corrected the numbers.  :-+


Input stage layout looks a bit lame, it seems needlessly sensitive to thermal gradients generated by the output stage. RC4558 (which this chip is probably equivalent to) has the input transistors horizontally; see zeptobars.

Yes this design doesn´t look very sophisticated...

Title: Re: Opamps - Die pictures
Post by: David Hess on February 12, 2021, 08:30:30 pm
I'm surprised how many (cheap) opamps use jfets inside. My understanding is, they are very unpredictable. At least discrete ones. So, does it mean jfets inside ICs have tighter tolerances, or circuits simply don't care if there is a, say, 5x variation to Idss?

Those are "pinch resistors" which implement a high resistance which is not otherwise practical.  They might be shown on the schematic as a JFET or resistor but sometimes you can find them marked as a resistor with a adjacent parallel bar connected to one end representing the JFET gate connection.

They are especially useful for startup circuits where poor tolerance is not a problem.

Title: Re: Opamps - Die pictures
Post by: magic on February 12, 2021, 10:18:29 pm
The term "pinch resistor" usually refers to resistors made of base material (P silicon) pinched by emitter material (N silicon) which also contacts the underlying collector silicon (N) on both sides of the P resistor. We have seen a ton of those on Noopy's images. They are indeed somewhat like P-JFETs and they saturate at higher voltages. The P-JFETs in BiFET processes are built in a similar manner, but are spread over more area and require higher fabrication precision than BJT bases and emitters. IIRC they had to use ion implantation for that, instead of diffusion.

The N-JFETs on traditional bipolar processes (epi-FETs) are long and narrow isolation islands surrounded by P substrate and P isolation walls and covered on top by (rather shallow) P base diffusion. So a different kind of structure, much larger and harder/impossible to fabricate with precision, and the gate is always the substrate.

Relevant drawing from old Signetics applications manual below.
Title: Re: Opamps - Die pictures
Post by: exe on February 13, 2021, 09:22:42 am
Ah, got it. What is the problem with creating high-value resistors in IC? I remember reading somewhere that one of challenges in early ICs was to design circuits with resistors in the range of, say, 1-10k.
Title: Re: Opamps - Die pictures
Post by: magic on February 13, 2021, 09:40:24 am
Because there is no highly resistive material available. Resistors on cheap ICs are made of doped silicon, and you don't want doped silicon to have too high resistance because you don't want 10kΩ in series with every transistor terminal :P

And of course you can make ristors of any value, they just need to be loooong.
Title: Re: Opamps - Die pictures
Post by: Noopy on February 13, 2021, 09:42:06 am
And so you have to integrate veeeeeery looooooong tracks.  ;D
Title: Re: Opamps - Die pictures
Post by: Noopy on March 04, 2021, 09:29:52 pm
(https://www.richis-lab.de/images/opamp/30x01.jpg)

ICL8007, a JFET-input general purpose opamp built by Intersil. Datecode 7429.


(https://www.richis-lab.de/images/opamp/30x03.jpg)

(https://www.richis-lab.de/images/opamp/30x08.jpg)

Intersil Data Book 1979


(https://www.richis-lab.de/images/opamp/30x09.jpg)

ICL8007 datasheet 1979
I don´t understand it. Different names and specs in every table.  |O :-//


(https://www.richis-lab.de/images/opamp/30x05.jpg)

There are different schematics for the version with external offset alignment and for the model without external offset alignment!
Most interesting is the blue input stage around the yellow/cyan differential stage. It is built so the voltage around the JFETs doesn´t vary to much with common mode voltage. With large Drain-Source-voltages the gate current would increasing.


(https://www.richis-lab.de/images/opamp/30x10.jpg)

(https://www.richis-lab.de/images/opamp/30x06.jpg)

The die is 2,1mm x 1,4mm.


(https://www.richis-lab.de/images/opamp/30x07.jpg)

BL8007, a typical Intersil naming.


(https://www.richis-lab.de/images/opamp/30x11.jpg)

There is a JFET test structure. Probably to check the JFET specifications outside the circuit.


(https://www.richis-lab.de/images/opamp/30x12.jpg)

There are some differences between the schematic and the die.


(https://www.richis-lab.de/images/opamp/30x13.jpg)

(https://www.richis-lab.de/images/opamp/30x14.jpg)

Input stage contains four cross connected JFETs for less temperature drift.


(https://www.richis-lab.de/images/opamp/30x15.jpg)

The voltage loop around the input JFETs looks a bit different. There are independent current sources. Instead there are the transistors Qx and Qy.


(https://www.richis-lab.de/images/opamp/30x16.jpg)

There are some options on the die. The currentsinks of the input stage contain two emitters but only one is connected. If you need more current you can connect the second emitter.


(https://www.richis-lab.de/images/opamp/30x17.jpg)

The current source of the second stage looks like it could be split in two sources. There are also two additional connections in the resistors over the current sources.
There is a third resistor connected to R5 but not connected on the other side. I don´t know what that one would be good for. Looks not very symmetrical.  :-//


https://www.richis-lab.de/Opamp29.htm (https://www.richis-lab.de/Opamp29.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on March 04, 2021, 09:55:34 pm
Aren't those FETs P channel, as you would expect on a basic BIFET process? That would explain the whole Qx / Qy thing - the FETs are just source followers, the BJTs are emitter followers that bootstrap their drains and also drive the PNPs where the actual opamp begins.
Title: Re: Opamps - Die pictures
Post by: Noopy on March 04, 2021, 09:58:30 pm
Damn it, I always take the wrong symbols! Of course that should be p-channel JFETs.  :-+
I will correct that tomorrow.
Thanks for the hint!  :-+
Title: Re: Opamps - Die pictures
Post by: magic on March 04, 2021, 10:23:02 pm
And there is another error. As drawn, the JFETs have exacly 0 volts on them because of Qx/Qy and D1/D2. That doesn't look like it would work ;)
It seems that resistors R3/R4 are actually between Qx/Qy and D1/D2 and the PNP input stage is connected directly to Qx/Qy.

And the "pinout" of the test JFET is labeled wrong if they are P channel.
Title: Re: Opamps - Die pictures
Post by: Noopy on March 04, 2021, 10:37:53 pm
Right!  :-+

...aaaaand done!  :-/O
Title: Re: Opamps - Die pictures
Post by: magic on March 10, 2021, 11:21:39 am
This took me a few hours but it had to be done :-DD

So what we've got here? The input stage is as we know it, the active loads turn out to be Darlington pairs. Precision is precision, I suppose. Followers Q9,Q10 drive the second stage and Q9 also drives the 1st stage load - this has been nicely simplified in the newer OPA827 according to the datasheet.

Lots of capacitors are sprinkled all over the area, mostly bypassing BE junctions of various transistors. Not sure what C3,C4 are doing but likely stabilizing the loop involving Q5~Q9. The actual compensation capacitors are C5,C6 - the segmented ones. We can guess what OPA637 looks like.

The second stage and output buffer are essentially as drawn in the datasheet. Curiously, Q19,Q20 have the same area as the outputs and Q21~Q23 shift their BE voltages exactly, so the output seems to run on equal bias as each branch of the second stage, even slightly less due to R18,R19 :wtf:

R21,J5 and the associated circuitry is the bias generator. J6,Q26,Q27 appear to be the patented circuit they call "noise free cascode". The mirror multiplies J6 current 16 times, reducing die area required for J6. Q30~Q35 looks like a "high feedback" mirror trying to accurately match Q35 current to J5 current. Q36,Q37 is a cascode current source that biases the input stage, Q38~Q41 bootstrap input JFET drains, as we know.

All she wrote :D

I'm still don't know what's the point of J3,J4 instead of doing it as drawn in the datasheet and in LM101A. Maybe one day. Indeed, the main point of this whole exercise was to find out how exactly they bias the input stage and whether some deeper trickery is involved. Apparently not, it's just a current source feeding the bases of Q1~Q4.
Title: Re: Opamps - Die pictures
Post by: Noopy on March 10, 2021, 07:51:07 pm
This took me a few hours but it had to be done :-DD

Thanks, very interesting!  :-+
Would it be ok for you if I post your schematic on my website?



Can anyone tell me who built this opamp?


(https://www.richis-lab.de/images/opamp/31x01.jpg)

(https://www.richis-lab.de/images/opamp/31x02.jpg)

TIC60005


(https://www.richis-lab.de/images/opamp/31x03.jpg)

(https://www.richis-lab.de/images/opamp/31x04.jpg)

05.T  :-//
Datecode probably 7017


(https://www.richis-lab.de/images/opamp/31x05.jpg)

(https://www.richis-lab.de/images/opamp/31x06.jpg)

The die is 1,3mm x 1,2mm.


(https://www.richis-lab.de/images/opamp/31x07.jpg)

That doesn´t really help...  :-//


(https://www.richis-lab.de/images/opamp/31x08.jpg)

The TIC60005 is quite similar to the NS LM709 (https://www.richis-lab.de/Opamp20.htm (https://www.richis-lab.de/Opamp20.htm)). But there are some differences.


(https://www.richis-lab.de/images/opamp/31x09.jpg)

At the input there are darlington transistors placed and connected crossover.
The crossover connection is often used with FETs connected in parallel to reduce temperature drift. In bipolar input stages that doesn´t help very much. But with serially connected darlington transistors crossover connection can be beneficial.


(https://www.richis-lab.de/images/opamp/31x10.jpg)

R11 has a additional connection over which they were able to adjust the current through the input stage.


(https://www.richis-lab.de/images/opamp/31x12.jpg)

(https://www.richis-lab.de/images/opamp/31x11.jpg)

In the output stage there are two additional transistor and one additional resistor working as an overcurrent protection.


https://www.richis-lab.de/Opamp30.htm (https://www.richis-lab.de/Opamp30.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on March 12, 2021, 04:37:47 pm
Can anyone tell me who built this opamp?
TIC60005

Have you ever heard of Transitron? The T with the scroll would fit.
They had a 709 variant but that was called TOA2709 or TOA4709. I will get these two soon and we will see what´s insinde.
Perhaps they marked the package specially for the customer or they changed a small part of the circuit...
Title: Re: Opamps - Die pictures
Post by: serg-el on March 12, 2021, 09:49:22 pm
Isn't it?
TAA521
UA709HC

http://www.wolfram-zucker.de/elektronik/bauelemente.htm?ics-analog.htm (http://www.wolfram-zucker.de/elektronik/bauelemente.htm?ics-analog.htm)
Title: Re: Opamps - Die pictures
Post by: Noopy on March 13, 2021, 04:07:41 am
I found this website too. In my view he just lists alternatives.

Here you can see a TOA2709:

https://www.nyabcz.com/index.php?main_page=product_info&products_id=308090 (https://www.nyabcz.com/index.php?main_page=product_info&products_id=308090)
Title: Re: Opamps - Die pictures
Post by: Noopy on March 24, 2021, 09:41:35 pm
(https://www.richis-lab.de/images/Opamp/32x01.jpg)

National Semiconductor LF356


(https://www.richis-lab.de/images/Opamp/32x04.jpg)

Interesting: It seems like the LF356 die is exactly the same as the LF355 die (https://www.richis-lab.de/Opamp15.htm (https://www.richis-lab.de/Opamp15.htm)). But the bandwith of the LF356 is much higher (5MHz vs. 2,5MHz).
I don´t think that is due to binning because there was alreading binning for the LF1xx and LF2xx.  :-//
Perhaps they modified the process parameters a bit for the LF356?  :-//


(https://www.richis-lab.de/images/Opamp/32x05.jpg)

Seems to be an old model. The LF355 built 1982 used the mask revisions BBBBDCBEH.


https://www.richis-lab.de/Opamp31.htm (https://www.richis-lab.de/Opamp31.htm)
Title: Re: Opamps - Die pictures
Post by: magic on March 24, 2021, 10:55:40 pm
Bandwidth and slew rate depend on input stage stage transconductance as much as on compensation capacitance.

Noise also depends on gm and it is specified worse for the 355, so the difference has to be in the input stage. Perhaps as simple as less bias current due to different size of a small resistor hidden somewhere.
Title: Re: Opamps - Die pictures
Post by: Noopy on March 25, 2021, 06:02:00 am
Sounds feasible.  :-+  Nevertheless I found no difference on the dies. And the numbers 156 on both dies make me believe it´s the same mask set. But of course that´s only a opinion.  :-//
Title: Re: Opamps - Die pictures
Post by: magic on March 25, 2021, 06:12:06 am
I had a look at the schematic and it seems that basing is accomplished by J10, J11 and J4 which are all IDSS current sources.
So one possibility is that 355 JFETs have lower IDSS, which I suspect could be a matter of doping concentration or diffusion depth. Maybe they just binned them.
Title: Re: Opamps - Die pictures
Post by: Noopy on March 25, 2021, 06:31:31 am
So one possibility is that 355 JFETs have lower IDSS, which I suspect could be a matter of doping concentration or diffusion depth. Maybe they just binned them.

Either binning or they modified the process a little. A little more dopant and you get the LF356. Something like that.  :-/O
Title: Re: Opamps - Die pictures
Post by: David Hess on March 25, 2021, 05:34:34 pm
There is also the LF357 which is the higher bandwidth decompensated version of the LF356 but with the same input noise implying the same operating currents which is confirmed by the datasheets.

Low power operation of the LF355 means that all of the stages operate with lower current which is easy enough to accomplish and that means lower transconductance on the differential input stage so higher noise.  Lower power dissipation also yields better DC characteristics.

Linear Technology made improved replacements in the form of the LT1055/LT1056 so there might be something to learn from their published schematics which show the current for each stage:

https://docs.rs-online.com/6232/0900766b810ed81d.pdf
Title: Re: Opamps - Die pictures
Post by: Noopy on March 25, 2021, 09:03:24 pm
There is also the LF357 which is the higher bandwidth decompensated version of the LF356 but with the same input noise implying the same operating currents which is confirmed by the datasheets.

Yes, the LF357 has a smaller compensation capacitor. Unfortunately I have no pictures of the LF357 but its higher bandwidth is quite explainable.


Low power operation of the LF355 means that all of the stages operate with lower current which is easy enough to accomplish and that means lower transconductance on the differential input stage so higher noise.  Lower power dissipation also yields better DC characteristics.

I haven´t realised that the supply current of the LF355 is lower.  :-+
A factor of 2,5... I don´t think that is only binning, do you?
Title: Re: Opamps - Die pictures
Post by: David Hess on March 27, 2021, 03:55:17 am
Low power operation of the LF355 means that all of the stages operate with lower current which is easy enough to accomplish and that means lower transconductance on the differential input stage so higher noise.  Lower power dissipation also yields better DC characteristics.

I haven´t realised that the supply current of the LF355 is lower.  :-+
A factor of 2,5... I don´t think that is only binning, do you?

No, that cannot be binning, but it is adjustable with a single resistor or fuse by changing the current source which drives the positive and negative rail current mirrors, although the currents given in the Linear Technology schematic imply that the current mirror ratios are different.
Title: Re: Opamps - Die pictures
Post by: Noopy on March 27, 2021, 07:38:37 am
Low power operation of the LF355 means that all of the stages operate with lower current which is easy enough to accomplish and that means lower transconductance on the differential input stage so higher noise.  Lower power dissipation also yields better DC characteristics.

I haven´t realised that the supply current of the LF355 is lower.  :-+
A factor of 2,5... I don´t think that is only binning, do you?

No, that cannot be binning, but it is adjustable with a single resistor or fuse by changing the current source which drives the positive and negative rail current mirrors, although the currents given in the Linear Technology schematic imply that the current mirror ratios are different.

But I can´t spot a difference on the dies.  :-// There is definitely no fuse.
I will try to take some better pictures. I hope I can find the LF355 in my archive...  ;D
Title: Re: Opamps - Die pictures
Post by: magic on March 27, 2021, 08:56:05 am
I'm telling you it's all about IDSS :P

Input stage bias is determined strictly by IDSS of J10/J11 because the input pair's current simply has nowhere else to go; the bases of the second stage sink very little. Whatever excess current is injected into the input pair by Q1, gets sunk by Q12 when second stage is overdriven above the bias point set by Q13.

Second stage bias is determined by IDSS of J4, which is mirrored 1:1 into Q8 collector and half of it is mirrored 1:4 by Q13 into Q7/Q8 emitters. As an aside, I'm not sure if it's great for ensuring transfer linearity of the second stage :-\

As a sanity check, let's verify that Ic(Q1) > IDSS(J10)+IDSS(J11), which clearly needs to be the case for my proposed scheme work.
Well, Ic(Q1) is simply the total IDSS(J4), from both its halves. Each half consists of two segments twice as wide and about 25% shorter than the four segments of either J10 or J11, so total channel width is the same and length is slightly shorter, it checks out.

Assuming 800µA second stage bias (taken from LT1055 FWIW), we get 400µA total J4/Q1 current. And slightly below 400µA trough the input stage; no idea how IDSS scales with channel length and too lazy to look it up :-//
Title: Re: Opamps - Die pictures
Post by: Noopy on March 27, 2021, 07:52:28 pm
I'm telling you it's all about IDSS :P

Acknowledged!  :-+
But how did they change the IDSS?  :-/O ...perhaps we will never know...
Title: Re: Opamps - Die pictures
Post by: Noopy on April 08, 2021, 05:14:34 am
TIC60005


We had this dubious TIC60005. Now I have a TOA2709 and a TOA4709 for you.
TOA1709 and TOA2709 are the 709 equivalents. The TOA1709 is specified for a wider temperature range.
TOA7709 and TOA8709 offer you darlington inputs (TOA7709 for a wider temperature range). With the lower input current these opamps were built to compete with FET input opamps like the LH0042 (https://www.richis-lab.de/Opamp24.htm (https://www.richis-lab.de/Opamp24.htm)). The TIC60005 is one of these.
There is no information about the TOA4709.  :-//



(https://www.richis-lab.de/images/Opamp/33x02.jpg)

TOA2709


(https://www.richis-lab.de/images/Opamp/33x04.jpg)

It´s the same design as used in the TIC60005.


(https://www.richis-lab.de/images/Opamp/33x06.jpg)

There are the darlington input transistors but only one row is connected to the circuit.


(https://www.richis-lab.de/images/Opamp/33x07.jpg)

(https://www.richis-lab.de/images/Opamp/33x08.jpg)

Two dead transistors and a molten track.  :o


(https://www.richis-lab.de/images/Opamp/33x09.jpg)

It seems like there was an low impedance overvoltage at one of the input compensation pins.



(https://www.richis-lab.de/images/Opamp/34x01.jpg)

TOA4709


(https://www.richis-lab.de/images/Opamp/34x02.jpg)

A familiar design.


(https://www.richis-lab.de/images/Opamp/34x06.jpg)

(https://www.richis-lab.de/images/Opamp/34x07.jpg)

But it looks like they changed the fabrication process. They not only changed the metal layer. The transistors are also a little different.


(https://www.richis-lab.de/images/Opamp/34x04.jpg)

It seems like the only difference between the TOA2709 and the TOA4709 is the overcurrent protection.


(https://www.richis-lab.de/images/Opamp/34x05.jpg)

There are some "bubbles" on the metal layer and this "hole" looks quite bad...  :o



Now some numbers:


(https://www.richis-lab.de/images/Opamp/33x05.jpg)

TOA2709
https://www.richis-lab.de/Opamp32.htm (https://www.richis-lab.de/Opamp32.htm)


(https://www.richis-lab.de/images/opamp/31x07.jpg)

TIC60005 (TOA8709)
https://www.richis-lab.de/Opamp30.htm (https://www.richis-lab.de/Opamp30.htm)


(https://www.richis-lab.de/images/Opamp/34x03.jpg)

TOA4709
https://www.richis-lab.de/Opamp33.htm (https://www.richis-lab.de/Opamp33.htm)


 :-/O
Title: Re: Opamps - Die pictures
Post by: exe on April 08, 2021, 09:05:12 am
TOA7709 and TOA8709 offer you darlington inputs (TOA7709 for a wider temperature range). With the lower input current these opamps were built to compete with FET input opamps like the LH0042 (https://www.richis-lab.de/Opamp24.htm (https://www.richis-lab.de/Opamp24.htm)).

What's their input bias? I found data for HA2605 which claimed to be an alternative to TOA8709. Its input bias current is 40nA which is very far from what fet inputs offer :/. But that's over the whole temperature range. I didn't find any typical data. I also didn't find a datasheet for TOA8709. Seems to be very old parts :)
Title: Re: Opamps - Die pictures
Post by: Noopy on April 08, 2021, 08:10:32 pm
TOA7709 and TOA8709 offer you darlington inputs (TOA7709 for a wider temperature range). With the lower input current these opamps were built to compete with FET input opamps like the LH0042 (https://www.richis-lab.de/Opamp24.htm (https://www.richis-lab.de/Opamp24.htm)).

What's their input bias? I found data for HA2605 which claimed to be an alternative to TOA8709. Its input bias current is 40nA which is very far from what fet inputs offer :/. But that's over the whole temperature range. I didn't find any typical data. I also didn't find a datasheet for TOA8709. Seems to be very old parts :)

I also didn´t find very much about these opamps. In "Electronics", December 1976 (archive.org) there is an article about the TOAx709 that states 10nA typical bias current. Of course FET inputs can do better at room temperature but at high temperature the TOAx709 were able to compete with FET input opamps. ...back in the days.
Title: Re: Opamps - Die pictures
Post by: magic on April 08, 2021, 08:33:56 pm
Funnily enough, they used to make JFET opamps with bias cancellation :wtf:

This is OP-15 from Precision Monolithics, supposedly an improved LF155. I learned about it while looking for information about the LF parts. Not sure how old it is exactly.

J11 gate leakage is mirrored into each input pin and input currents are guaranteed <10nA over temperature.

Title: Re: Opamps - Die pictures
Post by: Noopy on April 08, 2021, 08:44:25 pm
Funnily enough, they used to make JFET opamps with bias cancellation :wtf:

This is OP-15 from Precision Monolithics, supposedly an improved LF155. I learned about it while looking for information about the LF parts. Not sure how old it is exactly.

J11 gate leakage is mirrored into each input pin and input currents are guaranteed <10nA over temperature.

Very interesting! I haven´t seen such a compensation yet.  :-+
Title: Re: Opamps - Die pictures
Post by: David Hess on April 09, 2021, 01:48:02 am
Funnily enough, they used to make JFET opamps with bias cancellation :wtf:

This is OP-15 from Precision Monolithics, supposedly an improved LF155. I learned about it while looking for information about the LF parts. Not sure how old it is exactly.

J11 gate leakage is mirrored into each input pin and input currents are guaranteed <10nA over temperature.

I have my PMI databook right here and I am sure I have noticed that before.  I wonder if PMI's JFETs were particularly leaky.
Title: Re: Opamps - Die pictures
Post by: magic on June 14, 2021, 10:34:44 pm
Anyone remember ICL8007, the early JFET opamp so bad that it needed drain bootstraping and common centroid layout and still was quite bad? Recently zeptobars found its low cost competitor from Analog: guaranteed <20mV offset in the best grade ;D

https://zeptobars.com/en/read/AD540-Analog-Devices-FET-opamp

Similar P-JFETs in source follower configuration and then NPN emitter followers driving drain bootstrap resistors and a two stage bipolar opamp where the real action happens.
Title: Re: Opamps - Die pictures
Post by: Noopy on June 15, 2021, 03:07:31 am
Looks quite familiar!  :-+ ;D
Title: Re: Opamps - Die pictures
Post by: Noopy on June 18, 2021, 03:34:41 am
(https://www.richis-lab.de/images/Opamp/35x01.jpg)

ML709
Can anybody tell who manufactured these opamps?


(https://www.richis-lab.de/images/Opamp/35x02.jpg)

We often have seen this 709 design. This one is again a little different but quite similar.


(https://www.richis-lab.de/images/Opamp/35x05.jpg)

709 B? A second revision?


(https://www.richis-lab.de/images/Opamp/35x04.jpg)

The process to built such an old semiconductor is easy to understand. It is similar to the process involved in the LM306 (https://www.richis-lab.de/Opamp09.htm (https://www.richis-lab.de/Opamp09.htm)).
Mask 1 builds the buried n+ structures that later are used to connect the collector of the transistors.
n epi forms a uniform n layer on top of the buried n+ structures.
Mask 2 forms trenches in the n epi that isolate the active areas against each other.
Mask 4 forms the (p doped) base areas of the npn transistors and the resistors. It looks like this mask worked reversed. The color of the 4 is a little greyish and this color is everywhere except on top of the base areas and the resistors.
Mask 5 forms the highly n doped emitter areas and the connectors to the buried n+ structures.
Mask 6 generates vias.
Mask 8 forms the metal layer.
Done!  8)


https://www.richis-lab.de/Opamp34.htm (https://www.richis-lab.de/Opamp34.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on June 18, 2021, 07:51:51 am
Possibly these guys, same ML- part numbers and Roman date codes.

https://en.wikipedia.org/wiki/MicroSystems_International

The MIL723 could have been from there too - wasn't it sent to you from Canada?
Title: Re: Opamps - Die pictures
Post by: Noopy on June 18, 2021, 08:40:22 am
Sounds reasonable for both parts.  :-+

That´s interesting, you find some information about computer parts but I couldn´t find information about "normal" parts like the ML709.  :-//
Title: Re: Opamps - Die pictures
Post by: magic on June 18, 2021, 09:02:59 am
The company existed for five years in the 1970s so I am not very surprised that there is little information about it.

If you don't mind going to Canada, one museum has paper copies of their IC catalogues, including linear ;)
http://www.cse.yorku.ca/museum/collections/MIL/MIL.htm (http://www.cse.yorku.ca/museum/collections/MIL/MIL.htm)
Title: Re: Opamps - Die pictures
Post by: Noopy on June 18, 2021, 09:43:36 am
Next vacation has to be in Canada!  :-+ ;D
Title: Re: Opamps - Die pictures
Post by: Noopy on August 19, 2021, 04:59:18 am
(https://www.richis-lab.de/images/Opamp/36x01.jpg)

I got an UA741 manufactured by Tungsram.
No, it´s not a tube opamp.  ;D


(https://www.richis-lab.de/images/Opamp/36x02.jpg)

(https://www.richis-lab.de/images/Opamp/36x03.jpg)

We have already seen this design. It´s the same as in the National Semiconductor LM741: https://www.richis-lab.de/Opamp23.htm (https://www.richis-lab.de/Opamp23.htm)


https://www.richis-lab.de/Opamp35.htm (https://www.richis-lab.de/Opamp35.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on August 19, 2021, 06:00:10 am
Nice copy, even most test patterns are ripped off ;D

And you have posted wrong schematic. I have never seen a chip actually implementing the original Fairchild schematic and I'm starting to think that maybe the schematic was made up and no such chip ever existed. It wouldn't be the first time with Fairchild.

Most old 741 are implemented like this:
http://www.righto.com/2015/10/inside-ubiquitous-741-op-amp-circuits.html (http://www.righto.com/2015/10/inside-ubiquitous-741-op-amp-circuits.html)

And the Tungsram and National that you posted here follow the TI OP07 schematic.
Of course real OP07 are not like that, that's TI's FAIL :palm:

edit
You can see two old 741 opamps here, including supposedly Fairchild and supposedly one from 1972, but these people are biologists so I'm not sure if they can be fully trusted ;) They also have a µA709 and even µA702 so at least the parts are hopefully genuine. They say the chips are from their lab's stock of old spare parts for equipment, or at least that's what they said about the previous batch of ICs they posted.
https://resnicklab.wordpress.com/2013/05/14/meanwhile/ (https://resnicklab.wordpress.com/2013/05/14/meanwhile/)
Title: Re: Opamps - Die pictures
Post by: Noopy on August 19, 2021, 08:42:38 am
Nice copy, even most test patterns are ripped off ;D

Perhaps they bought the dies or the process? In my view it´s too similar for a copy...  :-/O


And you have posted wrong schematic.

You told me that already a long time ago.  :-+ I have added a hint in the text under the first die. There is a link to the LH0042 where I have added "the other LM741 schematics.
...I should add a another hin under the schematic...


You can see two old 741 opamps here, including supposedly Fairchild and supposedly one from 1972, but these people are biologists so I'm not sure if they can be fully trusted ;) They also have a µA709 and even µA702 so at least the parts are hopefully genuine. They say the chips are from their lab's stock of old spare parts for equipment, or at least that's what they said about the previous batch of ICs they posted.
https://resnicklab.wordpress.com/2013/05/14/meanwhile/ (https://resnicklab.wordpress.com/2013/05/14/meanwhile/)

 :-+
Title: Re: Opamps - Die pictures
Post by: dzseki on August 19, 2021, 10:15:49 am
Nice copy, even most test patterns are ripped off ;D

Perhaps they bought the dies or the process? In my view it´s too similar for a copy...  :-/O


I had a colleague who worked in the Tungsram factory as IC architect. He told me that the common parts were simply reverse engineered.
Title: Re: Opamps - Die pictures
Post by: Noopy on August 19, 2021, 10:24:33 am
Nice copy, even most test patterns are ripped off ;D

Perhaps they bought the dies or the process? In my view it´s too similar for a copy...  :-/O


I had a colleague who worked in the Tungsram factory as IC architect. He told me that the common parts were simply reverse engineered.

But this design ist really the same.

We have seen reverse engineering here:
https://www.richis-lab.de/prawez03.htm (https://www.richis-lab.de/prawez03.htm)
https://www.richis-lab.de/prawez02.htm (https://www.richis-lab.de/prawez02.htm)
vs.
https://www.richis-lab.de/apple.htm (https://www.richis-lab.de/apple.htm)

and here:
https://www.richis-lab.de/REF02.htm (https://www.richis-lab.de/REF02.htm)
vs.
https://www.richis-lab.de/REF02a.htm (https://www.richis-lab.de/REF02a.htm)

and here:
https://www.richis-lab.de/LM723_04.htm (https://www.richis-lab.de/LM723_04.htm)
vs.
https://www.richis-lab.de/LM723_05.htm (https://www.richis-lab.de/LM723_05.htm)

The design is always a little different.

 :-//
Title: Re: Opamps - Die pictures
Post by: magic on August 19, 2021, 10:57:43 am
There are differences. The 741W text on the right is missing, some test structures are missing, alignment of the borders of metal traces and silicon structures is a bit different in some places, ... ;)

You told me that already a long time ago.  :-+ I have added a hint in the text under the first die. There is a link to the LH0042 where I have added "the other LM741 schematics.
Found it. I guess I didn't scroll down far enough the first time.
But there is still a problem: the LM148 schematic doesn't show current mirror resistors.

BTW, there is apparently a Texas Instruments µA741 still in production and the schematic is the same as OP07. So that's where the wrong OP07 schematic came from, the only mystery is why and how :wtf:
https://www.ti.com/lit/ds/symlink/ua741.pdf (https://www.ti.com/lit/ds/symlink/ua741.pdf)
Title: Re: Opamps - Die pictures
Post by: Noopy on August 19, 2021, 11:51:25 am
There are differences. The 741W text on the right is missing, some test structures are missing, alignment of the borders of metal traces and silicon structures is a bit different in some places, ... ;)

Between the to 741 there are 8 years. In my view that changes are probably connected with changes in the production process or fabrication of a new mask due to deterioration.
Naturally I´m not 100% sure...


You told me that already a long time ago.  :-+ I have added a hint in the text under the first die. There is a link to the LH0042 where I have added "the other LM741 schematics.
Found it. I guess I didn't scroll down far enough the first time.
But there is still a problem: the LM148 schematic doesn't show current mirror resistors.

You are right the LM148 schematic doesn´t fit perfectly too.
I should sneak through the die and create a new schematic but I find it hard to read.  :-\
Title: Re: Opamps - Die pictures
Post by: magic on August 19, 2021, 04:44:22 pm
TI is a good starting point. Find three differences from the original ;D

The chip is not too hard to follow given a schematic. There is the input NPNs, mirror driver above them, the input PNPs next to them, the mirror next. Then the output PNP and the PNP VAS buffer (these PNPs have substrate collectors). Next is the output NPN and VCC.
The structures left of OUT and above VCC are resistors combined with current limiting transistors. Another trick is an NPN diode on top of one of the collectors of the split collector PNP. The rest shouldn't be rocket science.
Title: Re: Opamps - Die pictures
Post by: David Hess on August 19, 2021, 05:41:10 pm
Published schematics almost always leave things out.  For instance they only very rarely show the various special transistor variations or pinch resistors.  As far as errors in schematics, I suspect sometimes they are deliberate.

I got an UA741 manufactured by Tungsram.

The packaging style and printing look like Fairchild of that era.
Title: Re: Opamps - Die pictures
Post by: Noopy on August 19, 2021, 05:46:38 pm
The chip is not too hard to follow given a schematic.

In principle you are right but somehow I don´t like this die...  ;D


I got an UA741 manufactured by Tungsram.

The packaging style and printing look like Fairchild of that era.

Fairchild package look quite similar but here we have a T not a F. I have no open Fairchild 741 but the web tells us they had a different design.
Title: Re: Opamps - Die pictures
Post by: dzseki on August 19, 2021, 08:36:25 pm
Quote
I got an UA741 manufactured by Tungsram.

The packaging style and printing look like Fairchild of that era.

Fairchild package look quite similar but here we have a T not a F. I have no open Fairchild 741 but the web tells us they had a different design.

I was told that when the IC production begun the base technology was licensed by Fairchild. In the early 80's the semiconductor division of Tungsram was rebranded as MEV, at that point the printing have also changed somewhat.
Title: Re: Opamps - Die pictures
Post by: Noopy on November 03, 2021, 04:05:17 am
(https://www.richis-lab.de/images/Opamp/37x01.jpg)

Microsystems International ML741, another µA741 variant built 1973.


(https://www.richis-lab.de/images/Opamp/37x02.jpg)

(https://www.richis-lab.de/images/Opamp/37x03.jpg)

(https://www.richis-lab.de/images/Opamp/37x04.jpg)

Nothing special to see but it´s a completely different die compared to the other 741 variants I have documented.


(https://www.richis-lab.de/images/Opamp/37x05.jpg)

741A, perhaps the first revision?


https://www.richis-lab.de/Opamp36.htm (https://www.richis-lab.de/Opamp36.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on November 03, 2021, 08:13:45 am
Another 101A input stage and it looks like common mode input range includes VCC this time :o
Somebody saved one diode.
Title: Re: Opamps - Die pictures
Post by: Noopy on November 03, 2021, 08:44:15 am
Yeah, the input stage looks funny.  :-+  ;D
Should be similar to the LM741. Not similar to the schematic in the datasheet of the LM741 but similar to the schematic in the datasheet of the LM148 what describes the LM741 more correct:

(https://richis-lab.de/images/Opamp/25x09.jpg)

https://richis-lab.de/Opamp24.htm (https://richis-lab.de/Opamp24.htm)
Title: Re: Opamps - Die pictures
Post by: Noopy on December 10, 2021, 04:59:38 am
(https://www.richis-lab.de/images/Opamp/38x01.jpg)

I wanted to take a look into a OPA541AP to see if it is the same as the OPA541BM (https://www.richis-lab.de/Opamp02.htm (https://www.richis-lab.de/Opamp02.htm)).


(https://www.richis-lab.de/images/Opamp/38x02.jpg)

It is the same die, nothing special to see...


https://www.richis-lab.de/Opamp37.htm (https://www.richis-lab.de/Opamp37.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on December 10, 2021, 05:31:34 am
Looks like beefed up OPA445 - same schematic (but with Darlington outputs), same output NPN cells, same trick with two capacitors in series (for high breakdown voltage, presumably).
OPA445 is one of the fake OPA627 found by zeptobars years ago. I spent a few hours identifying it and it turns out a big hint was already in this thread.
Oh well :palm: :D
Title: Re: Opamps - Die pictures
Post by: Noopy on December 10, 2021, 08:00:58 am
Yeah, they look like brothers!  :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on December 18, 2021, 03:37:00 pm
Mini-Update

I found a nice Transitron ad for their µA709 variants:

(https://www.richis-lab.de/images/Opamp/31x13.jpg)


https://www.richis-lab.de/Opamp30.htm#Update (https://www.richis-lab.de/Opamp30.htm#Update)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on December 22, 2021, 04:19:30 am
(https://www.richis-lab.de/images/Opamp/39x01.jpg)

(https://www.richis-lab.de/images/Opamp/39x02.jpg)

(https://www.richis-lab.de/images/Opamp/39x03.jpg)

Q67A3S3? I didn´t find any information about this part.  :-//
The bigger T looks like Toshiba. We have seen that on the TA75558 package: https://www.richis-lab.de/Opamp28.htm (https://www.richis-lab.de/Opamp28.htm)


(https://www.richis-lab.de/images/Opamp/39x04.jpg)

(https://www.richis-lab.de/images/Opamp/39x05.jpg)

(https://www.richis-lab.de/images/Opamp/39x06.jpg)

It´s a µA709 mutation! It looks quite similar to the LM709: https://www.richis-lab.de/Opamp20.htm (https://www.richis-lab.de/Opamp20.htm)
There is no pointer to the manufacturer.  :-//
Interesting point: They have put wide metal lines around the left, lower and right edge. Some lines are broadened and lengthened to achieve this. At the right edge there is an isolated metal line.


https://www.richis-lab.de/Opamp38.htm (https://www.richis-lab.de/Opamp38.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: floobydust on December 22, 2021, 04:58:23 am
EDN July 1967 (https://archive.org/details/bitsavers_ElectronicignV15N1519670719_89698820/page/58/mode/2up?q=709) has Fairchild, Motorola, Raytheon (issue cover) 709 die pics.
I didn't know the 709 op-amp was such a big deal, hitting the market Nov. 1965 and production maxxed out on 2" wafers. Bob Widlar leading the pack.
Title: Re: Opamps - Die pictures
Post by: Noopy on December 28, 2021, 08:47:29 pm
(https://www.richis-lab.de/images/Opamp/40x01.jpg)

Texas Instruments TLC272, a Dual Opamp with MOSFET-Inputs.
A single supply between 3V and 16V is enough. Typical Vos is 230µV (TLC272BC, 25°C) with a TC of 1,8µV/°C. Bias current is 0,6pA typ (25°C). Bandwidth goes up to 1,3MHz - 3,4MHz depending on the variant, supply voltage and temperature.
Datasheet mentions a TLC277 with a little lower Vos: 200µV typ, 500µV max (2000µV max for the TLC272BC).


(https://www.richis-lab.de/images/Opamp/40x06.jpg)

There is a schematic in the datasheet. I have added some colors.
The green circuit is the differential pair input amplifier. The zener D1 in the current mirror seems to be a current limit. In normal operation a current limitation is not necessary but at startup it´s possible that the current source P3 puts out more current than is good for the mirror for it.
The yellow circuit is the voltage amplifier. D2 is for the bias limits the output to N4. R5 and C1 are the feedback path.
In the red output stage the highside transistor is connected to the output of the VAS while the lowside transistor is connected to the input of the VAS where the signal is 180° out of phase. The output of the TLC272 can be shorted without damage. With the limiting diode D2 the lowside transistor is safe. In the supply line of the highside transistor they added the resistor R6.
The blue circuit is the bias generator. P5/P6 and N6/N7 generate the reference voltage that controls the current sources P3 and P4.


(https://www.richis-lab.de/images/Opamp/40x08.jpg)

Since Texas Instruments sold the TLC272Y as bare die too there is a picture of the die in the datasheet.


(https://www.richis-lab.de/images/Opamp/40x03.jpg)

(https://www.richis-lab.de/images/Opamp/40x02.jpg)

The die in the TLC272 looks like the circuit in the datasheet.
Texas called the technology "Silicongate LinCMOS".


(https://www.richis-lab.de/images/Opamp/40x04.jpg)

Designed 1997.


(https://www.richis-lab.de/images/Opamp/40x05.jpg)

At the lower edge there is the name TLC272D. D could be a revision. In the datasheet you can see a TLC272C.


(https://www.richis-lab.de/images/Opamp/40x16.jpg)

There are two small "symbols" on the die. These parts of the metal layer are not connected to anything. Perhaps really small initials?


...
Title: Re: Opamps - Die pictures
Post by: Noopy on December 28, 2021, 08:48:32 pm
(https://www.richis-lab.de/images/Opamp/40x07.jpg)

You can find every part of the schematic on the die. Especially interesting are the input transistors P1/P2 and the current mirror transistors N1/N2. There are four times four input transistors criss-cross connected for low TC of Vos. N1/N2 are less meshed but still criss-cross connected.
In the middle of the die there is the biasing circuit which is used by both opamps, the right one and the left one.
At the lower edge there is the output stage.


(https://www.richis-lab.de/images/Opamp/40x09.jpg)

The output bondpad and the Vdd bondpad are equipped with a ESD protection MOSFET. While the "normal" MOSFETs have silicon gates this one has a metal gate. The thicker gate oxide increases the threshold voltage so that the MOSFET conducts at higher voltages. The line into the opamp circuit isn´t connected directly to the bondpad but to the doped area of the MOSFETs. That gives you a little higher impedance for an ESD pulse.


(https://www.richis-lab.de/images/Opamp/40x10.jpg)

At the input bondpads there is an additional protection with a series resistor and a small component, probably a zener diode.


(https://www.richis-lab.de/images/Opamp/40x11.jpg)

The input MOSFETs have circular gate electrodes.
The criss-cross connection made the interconnection quite complex.


(https://www.richis-lab.de/images/Opamp/40x13.jpg)

The n-MOS of the current mirror have bigger gate electrodes than the p-MOS at the input. Interesting...


(https://www.richis-lab.de/images/Opamp/40x12.jpg)

The source resistors of the current mirror are placed left of the transistors. The datasheet describes a "Trimmed Offset Voltage". If you want to tune Vos you have to tune these source resistors but it´s impossible to tune resistors this small.  :-// And I didn´t find an other tunable circuit on the die.  :-//
In the line under "Trimmed Offset Voltage" the datasheet describes the Vos of the TLC277. Perhaps the TLC277 die is different and tuneable.
In the upper right corner there are the two zener diodes.


(https://www.richis-lab.de/images/Opamp/40x14.jpg)

Lowside current mirror of the reference circuit.


(https://www.richis-lab.de/images/Opamp/40x15.jpg)

At the lower edge of the picture there is the highside current mirror.
The two big transistors on the left side are the two current sources for the left opamp (...on the right side for the right opamp).
Between the current sources there are some smaller transistors not shown in the schematic. That´s probably a startup circuit.


(https://www.richis-lab.de/images/Opamp/40x17.jpg)

The feedback resistor R5 is interesting: It travels a long way through the circuit.


(https://www.richis-lab.de/images/Opamp/40x18.jpg)

The feedback capacitor C1 is built with three electrodes. The output (green) is connected to the upper and the lower electrode (blue). The resistor R5 is connected to the electrode in the middle (red). The upper electrode is split and connected with a metal rectangular (black). That´s probably a way to tune the capacitance.


(https://www.richis-lab.de/images/Opamp/40x19.jpg)

The highside transistor (red) and the lowside transistor (blue) are integrated in the same area. The highside transistor is a little bigger.


(https://www.richis-lab.de/images/Opamp/40x20.jpg)

The resistor R6 is a wide stripe between the output transistor and Vdd (red). There is a metal plate on top of this resistor. The plate is connected to Vdd with a resistor (yellow). On the right side there is a strange part (green) between the plate and Vdd.  :-//
My best guess is that this metal is kind of a gate electrode that bias the resistor.  :-//


https://www.richis-lab.de/Opamp39.htm (https://www.richis-lab.de/Opamp39.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: David Hess on December 28, 2021, 10:05:26 pm
The n-MOS of the current mirror have bigger gate electrodes than the p-MOS at the input. Interesting...

To equalize gate capacitance for similar dynamic performance?

Quote
The highside transistor (red) and the lowside transistor (blue) are integrated in the same area. The highside transistor is a little bigger.

The p-channel transistors need to be larger for the same channel resistance and transconductance.  Even so, the datasheet reports a high side dropout that is a lot greater than the low side dropout.
Title: Re: Opamps - Die pictures
Post by: magic on December 28, 2021, 10:51:55 pm
Nice. I have a bunch of TS27L2, which is ST's version of the low power variant ("L"). The single (TLC/TS271) has a pin for adjusting internal bias and performance, offset nulling is available as well. I use them instead of LM358 when power consumption matters and I want to use THT because too lazy to make a custom PCB. They also have better "typical" precision specs than the cheapest of bipolar parts, thanks no doubt to the complex cross-coupling of 1st stage transistors.

D2 may be involved in output sink current limiting (by clamping Vgs of N4), what's the point of D1 I don't know. Not sure if I buy the theory that P3 can source more current than is safe for the mirror.

The n-MOS of the current mirror have bigger gate electrodes than the p-MOS at the input. Interesting...
This means more effective channel length. And also less channel width, because the central circle has less circumference. Both have some influence on characteristics of the FET, I think higher drain output impedance or something like that.

There is this article with some information about CMOS opamp design, including what AFAIK is the classic R2R output stage still used to this day in most chips.
http://class.ece.iastate.edu/djchen/EE501/2011/MonticelliRailToRailOutSwing.pdf (http://class.ece.iastate.edu/djchen/EE501/2011/MonticelliRailToRailOutSwing.pdf)


The p-channel transistors need to be larger for the same channel resistance and transconductance.  Even so, the datasheet reports a high side dropout that is a lot greater than the low side dropout.
This is not an R2R output, both transistors are N-channel, top is source follower.

It's a single supply opamp. And it struggles with sinking current when input common mode is near ground, which I believe is because source potential of P1/P2 limits the maximum gate voltage that can be applied to N4.
Title: Re: Opamps - Die pictures
Post by: Noopy on December 29, 2021, 06:55:35 am
...TS27L2, which is ST's version...

I will have to take a look into this one too.  :D


D2 may be involved in output sink current limiting (by clamping Vgs of N4), what's the point of D1 I don't know. Not sure if I buy the theory that P3 can source more current than is safe for the mirror.

You are right, the big current mirror probably won't get hurt but the current source P3 could kill itself.
D2 for output current limit? Hm, I'm not sure about that... For me that looks more like a bias voltage generator for the VAS.


It's a single supply opamp. And it struggles with sinking current when input common mode is near ground, which I believe is because source potential of P1/P2 limits the maximum gate voltage that can be applied to N4.

 :-+
Title: Re: Opamps - Die pictures
Post by: magic on December 29, 2021, 08:47:36 am
Monticelli states on page 4 that similar diode (Z1) is used to limit output current in LMC660. There is a similar Z2 at the high side P-MOS too, but not mentioned in the text.

VAS bias is set by the current source P4, as usual. The input stage will drive N3 to exactly sink all P4 current so that N5 source follower gate voltage stays where it needs to be. Output bias is determined by N4 being driven in parallel with N3. N4 is maybe 10x larger so it sinks 10x the VAS current. When the output is unloaded (or sourcing) that current will come from N5.
Title: Re: Opamps - Die pictures
Post by: Noopy on December 29, 2021, 09:19:16 am
I agree with your explanation and Mr. Monticelli paper.
Thanks for the correction.
 :-+

Title: Re: Opamps - Die pictures
Post by: Noopy on January 01, 2022, 06:23:50 pm
(https://www.richis-lab.de/images/Opamp/41x01.jpg)

We have talked about the TLC272. If you need more opamps you can take the TLC274 with four of them.
If you need a lower Vos you take the TLC279. Interesting point: The TLC279 has a higher Vos than the TLC277.


(https://www.richis-lab.de/images/Opamp/41x03.jpg)

In the datasheet you find a picture of the metal layer. Nice!  8)


(https://www.richis-lab.de/images/Opamp/41x02.jpg)

The die looks quite similar to the picture of the metal layer.


(https://www.richis-lab.de/images/Opamp/41x05.jpg)

TI doubled the TLC272. There are just a few differences.


(https://www.richis-lab.de/images/Opamp/41x04.jpg)

TLC274B, the picture in the datasheet shows a revision H!  :o


(https://www.richis-lab.de/images/Opamp/41x08.jpg)

I was right! These "things" we have already seen in the TLC272 are symbols! That´s a H and a fat I?


(https://www.richis-lab.de/images/Opamp/41x11.jpg)

Beside the GND bondpad there is a testpad with a single transistor. Source and Gate are connected to GND.


(https://www.richis-lab.de/images/Opamp/41x10.jpg)

The bulk of the input transistors (right) are connected with Vdd more massively than in the TLC272
Generally the transistors are connected more massively.


(https://www.richis-lab.de/images/Opamp/41x06.jpg)

Here we have the two source resistors (green), the capacitor (red) and the VAS transistor (cyan) we know from the TLC272. Everything is a little different but not in principle.


(https://www.richis-lab.de/images/Opamp/41x07.jpg)

The bias circuit can be found in the middle of the die.


(https://www.richis-lab.de/images/Opamp/41x09.jpg)

Here we have the highside current mirror of the reference circuit on the right side and the much smaller lowside current mirror on the left side. Between the current mirrors there is the circuit that probably guarantees a proper startup.


(https://www.richis-lab.de/images/Opamp/41x15.jpg)

Left and right of the reference circuit there are the current source transistors.


(https://www.richis-lab.de/images/Opamp/41x14.jpg)

(https://www.richis-lab.de/images/Opamp/41x12.jpg)

And here we have the obscure circuit that we have seen in the TLC272 too.
There is a strange element (blue) connected to Vdd directly and connected to Vdd through a resistor (red).
With this picture we can be sure that the circuit doesn´t influence the resistor R6 since the resistor is too far away (cyan).
Here we have two testpads to contact the strange element.


(https://www.richis-lab.de/images/Opamp/41x13.jpg)

On the right side of the die there is the same circuit.
But what the hell is the point of this circuit???   :-//


https://www.richis-lab.de/Opamp40.htm (https://www.richis-lab.de/Opamp40.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on January 01, 2022, 07:35:12 pm
eBay strikes again :-DD

Any chance that the mystery circuit is some sort of ESD protection? Like clamping overvoltage on VDD? I recall seeing such things in datasheets.
BTW, I found official schematic of LinCMOS per-pin protection in TLC3072 datasheet, but nothing about overvoltage protection.
Title: Re: Opamps - Die pictures
Post by: Noopy on January 02, 2022, 10:24:30 am
I thought about some overvoltage protection too but that would be placed near the Vdd pad and there is already a ESD protection.
Perhaps that is a circuit that is needed at the output stages. That would explain why these two "things" are placed at the left and right edge. A strange parasitic behaviour of the output stage? Removing free charges?  :-//
Title: Re: Opamps - Die pictures
Post by: Noopy on January 05, 2022, 04:25:29 am
(https://www.richis-lab.de/images/Opamp/42x01.jpg)

SN72709, another µA709 variant built by Texas Instruments.
The N stands for the epoxy package.


(https://www.richis-lab.de/images/Opamp/42x02.jpg)

Yeah, that´s a 709. There is nothing special.


(https://www.richis-lab.de/images/Opamp/43x01.jpg)

The specs of the AN variant are a little better.


(https://www.richis-lab.de/images/Opamp/43x02.jpg)

The die is the same. Texas Instruments did just some binning.


https://www.richis-lab.de/Opamp41.htm (https://www.richis-lab.de/Opamp41.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: David Hess on January 05, 2022, 05:24:28 am
I am always surprised that the 709 was as popular as it was considering its quirks and difficulty in using it safely.  Walter Jung discussed its history (https://www.analog.com/media/en/training-seminars/design-handbooks/Op-Amp-Applications/SectionH.pdf) a little bit.
Title: Re: Opamps - Die pictures
Post by: Noopy on January 05, 2022, 09:59:48 am
Well it looks like back in the days it was good enough. Seems it was one of the beststeller.
Title: Re: Opamps - Die pictures
Post by: MegaVolt on January 24, 2022, 11:41:14 am
Do you plan to photograph ADA4530? Or was it possible to celebrate photos on the Internet?
Title: Re: Opamps - Die pictures
Post by: Noopy on January 24, 2022, 11:53:56 am
Looks like an interesting part.  :-+ I can put it on my list. Right now it seems like you can´t by it anywhere...
Title: Re: Opamps - Die pictures
Post by: Noopy on February 13, 2022, 08:07:25 pm
(https://www.richis-lab.de/images/Opamp/44x01.jpg)

(https://www.richis-lab.de/images/Opamp/44x02.jpg)

(https://www.richis-lab.de/images/Opamp/44x03.jpg)

SGS ATEX L141, another µA741 mutation.


(https://www.richis-lab.de/images/Opamp/44x04.jpg)

Datasheet shows the same schematic as printed in the datasheet of the National Semiconductor LM741 (https://www.richis-lab.de/Opamp23.htm (https://www.richis-lab.de/Opamp23.htm)).
(It´s not the circuit integrated in the LM741.  :))


(https://www.richis-lab.de/images/Opamp/44x05.jpg)

(https://www.richis-lab.de/images/Opamp/44x06.jpg)

The bondwire of the positive supply has seen a little too much current.


(https://www.richis-lab.de/images/Opamp/44x07.jpg)

The die is quite similar to the Sescosem SC2741 (https://www.richis-lab.de/Opamp07.htm (https://www.richis-lab.de/Opamp07.htm)). Perhaps they worked together. Sescosem became Thomson Semiconductor and merged with SGS.

I don´t see major damage. The color of the bondpad in the lower right corner is a little strange but that´s probably just a process weakness.


(https://www.richis-lab.de/images/Opamp/44x08.jpg)

R4 defines the current in the differential input stage and in the L141 it can be adjusted.


https://www.richis-lab.de/Opamp42.htm (https://www.richis-lab.de/Opamp42.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: T3sl4co1l on February 13, 2022, 09:47:18 pm
Is that maybe some melty metallization on the top edge, towards the left?  Not sure what that is, if it's just some odd structure or actually kinda balled up.  Yeah, no or not obvious damage, after all the bondwire broke first so the die can't be toooo cooked.  I wonder if that would require reverse biasing (i.e. a mere diode drop into whatever other pins), maybe someone wired it wrong. ;D

Tim
Title: Re: Opamps - Die pictures
Post by: Noopy on February 14, 2022, 05:04:30 am
Is that maybe some melty metallization on the top edge, towards the left?

I don´t think so, but I´m not sure too.  :-//


I wonder if that would require reverse biasing (i.e. a mere diode drop into whatever other pins), maybe someone wired it wrong. ;D

That sounds very plausible to me.  :-+

Title: Re: Opamps - Die pictures
Post by: mawyatt on February 14, 2022, 02:39:01 pm
I wonder if that would require reverse biasing (i.e. a mere diode drop into whatever other pins), maybe someone wired it wrong. ;D

Tim

Think this is what happened since the apparent VCC wire bond melted. VEE should be the die substrate which can handle significant current.

Best,
Title: Re: Opamps - Die pictures
Post by: Noopy on February 23, 2022, 08:26:01 pm
(https://www.richis-lab.de/images/Opamp/45x01.jpg)

One more comparator, the Fairchild µA311. Single supply 5V-36V is possible. Like the LM306 (https://www.richis-lab.de/Opamp09.htm (https://www.richis-lab.de/Opamp09.htm)) the µA311 can drive a load directly. It can isolate 50V conduct 50mA and is protected against short circuits for 10s.


(https://www.richis-lab.de/images/Opamp/45x02.jpg)

The datasheet contains a schematic. I have colored it. The input stage contains additional resistors to do offset compensation. Datasheet explains you alternatively can use this inputs to rise the bias current and with it the slew rate.

There are two more stages (pink/grey) working with an bias current generated with Q23 and Q21 (blue). The current sinks are based on a reference voltage generator (yellow).

The output of the grey stage can be drained with Q7 (red). That´s the strobe feature. The cyan stage locks itself.

The output stage (dark red) contains the driver transistor Q12 and the output transistor Q15. The green circuit is the current limit. The purple circuit makes sure the driver transistor isn´t driven too hard so is still can be switched off fast.


(https://www.richis-lab.de/images/Opamp/45x03.jpg)

(https://www.richis-lab.de/images/Opamp/45x04.jpg)

The die is 1,6mm x 1,2mm. At the lower edge there are some test structures. In the upper right corner there is a test transistor.

On the right side there is the huge output transistor. You can see an additional frame probably similar to the LM306 output transistor, probably a base doping, a light p doping rising the breakdown voltage.


https://www.richis-lab.de/Opamp43.htm (https://www.richis-lab.de/Opamp43.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on February 27, 2022, 06:52:07 pm
(https://www.richis-lab.de/images/Opamp/46x01.jpg)

The PMI OP400 contains four opamps and is now built by Analog Devices. The offset voltage is 150µV typ. The current consumption is 725µA max. Open Loop Gain is 5000V/mV. Bias current is just 3nA (bipolar input) and you are allowed to load the output with 10nF.


(https://www.richis-lab.de/images/Opamp/46x02.jpg)

The schematic you can find in the datasheet.


(https://www.richis-lab.de/images/Opamp/46x03.jpg)

The die is 4,5mm x 3,1mm. You can clearly see the four opamps.


(https://www.richis-lab.de/images/Opamp/46x04.jpg)

In the center of the die there is the reference for the bias current sources.


(https://www.richis-lab.de/images/Opamp/46x05.jpg)

In the middle of each opamp you can see the four criss-cross connected input transistors (red). They look a little like PNP but they are NPN.
You can also find a small transistor with two emitter (green) which source some bias current.
The voltage limiting network is marked with a white arrow.

In the lower area there are two testpads which were probed. It looks like you can check the offset in the voltage amplifier stage.

In the upper left corner there are the big structures of the output stage.


https://www.richis-lab.de/Opamp44.htm (https://www.richis-lab.de/Opamp44.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: David Hess on February 28, 2022, 12:23:45 am
The PMI OP400 contains four opamps and is now built by Analog Devices. The offset voltage is 150µV typ. The current consumption is 725µA max. Open Loop Gain is 5000V/mV. Bias current is just 3nA (bipolar input) and you are allowed to load the output with 10nF.

The datasheet says quad OP-77 type performance, so equivalent to the improved generation which replaced the OP-07 like the LT1001 and later.  The OP-07 suffered from some performance problems that were resolved in its improved replacements.
Title: Re: Opamps - Die pictures
Post by: magic on February 28, 2022, 10:05:19 am
You can also find a small transistor with two emitter (green) which source some bias current.
two collectors ;)
This is the input bias cancellation circuit. The triple NPN rotated 90° runs on equal emitter current as the input pair, its base current is reflected by the PNP mirror to the left of the green arrow transistor and split in half by the green arrow transistor to be delivered to the input pins.

In the lower area there are two testpads which were probed. It looks like you can check the offset in the voltage amplifier stage.
These are zener zaps for adjustment of input stage load resistors right above them.

The datasheet says quad OP-77 type performance, so equivalent to the improved generation which replaced the OP-07 like the LT1001 and later.  The OP-07 suffered from some performance problems that were resolved in its improved replacements.
I thought that LT1001 is more or less an accurate clone of OP07.
It certainly doesn't have the guaranteed 114dB voltage gain spec of OP77 (or OP400).
Title: Re: Opamps - Die pictures
Post by: Noopy on March 01, 2022, 05:48:08 am
You can also find a small transistor with two emitter (green) which source some bias current.
two collectors ;)
This is the input bias cancellation circuit. The triple NPN rotated 90° runs on equal emitter current as the input pair, its base current is reflected by the PNP mirror to the left of the green arrow transistor and split in half by the green arrow transistor to be delivered to the input pins.

You are right! Thanks!  :-+


In the lower area there are two testpads which were probed. It looks like you can check the offset in the voltage amplifier stage.
These are zener zaps for adjustment of input stage load resistors right above them.

Indeed! I didn´t see this. Thanks again! I have taken some more pictures:


(https://www.richis-lab.de/images/Opamp/46x06.jpg)

(https://www.richis-lab.de/images/Opamp/46x07.jpg)

You can even see the short of the zapped zeners (the lower two).  :-+


https://www.richis-lab.de/Opamp44.htm#Update (https://www.richis-lab.de/Opamp44.htm#Update)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on March 01, 2022, 06:36:03 am
Well, zener zapping is mentioned on the first page of the datasheet so it had to be somewhere ;)
A quick look at the photograph confirms that those diodes are in parallel with resistors.
Title: Re: Opamps - Die pictures
Post by: Noopy on March 01, 2022, 06:38:05 am
Well, zener zapping is mentioned on the first page of the datasheet so it had to be somewhere ;)
A quick look at the photograph confirms that those diodes are in parallel with resistors.

Absolutely right!  :-+ :-+
Title: Re: Opamps - Die pictures
Post by: David Hess on March 02, 2022, 08:46:16 pm
The datasheet says quad OP-77 type performance, so equivalent to the improved generation which replaced the OP-07 like the LT1001 and later.  The OP-07 suffered from some performance problems that were resolved in its improved replacements.

I thought that LT1001 is more or less an accurate clone of OP07.
It certainly doesn't have the guaranteed 114dB voltage gain spec of OP77 (or OP400).

No, the LT1001 is a generation after the OP-07, which is consistent with timing and the fact that George Erdi designed both and said so.

Looking through Linear's selection guide, it does not appear that they ever released an improved replacement for the LT1001.  I wonder how reliable those open loop voltage gain specifications are.
Title: Re: Opamps - Die pictures
Post by: magic on March 03, 2022, 07:37:57 am
LT1001 precision specs are on par with OP77 and the low grade is similar to high grade OP07, but I assumed that these are things that could be down to details like better layout, more repeatable manufacturing or more zener trimming. They also tamed the dependence of Iq on Vs somewhat.

OP77 is supposed to have more DC gain, but you will only feel it a 0.1Hz, and - perhaps more usefully - 3x better typical AC CMRR at all frequencies.
OP400 has lousy DC specs in comparison, but surprisingly high AC CMRR.

Not sure where CMRR differences are coming from, but OP400 suggests maybe it's high input stage gain? :-//
Title: Re: Opamps - Die pictures
Post by: Kleinstein on March 03, 2022, 09:28:56 am
AC CMRR usually does not depend much on the open loop gain. Much is related to the GBW and how the compensation is done. The curves in the OP400 data-sheet look a bit odd and not really consistent: the AC CMRR is somewhat curved and would suggest deviation from simple dominant pole compensation, while the open loop gain / phase looks like simple ideal dominant pole compensation.

In the frequency domain the higher DC gain is visible only at very low frequency, but when looking in the time domain it still makes a difference after relatively short time (e.g. sub ms range).

The circuit for the input current cancelaton also helps a lot with CMRR, as it includes a kind of cascode for the input transistors. The LT1001 seems to use one more stage here. Some difference could also be from the biasing current source here.

The open loop gain can be a tricky part in the specs, as there is also ouput stage cross over. So the gain is not constant, but can change depending on the operation point. Besides that the gain should be relatively stable and not vary that much. There are a few resostors that can effect it, but nothing dramatic. I think the gain specs should be for the more normal operation points and not the possibly worst case cross over range.
Good DC gain can help to keep the error from the output cross over small.
Title: Re: Opamps - Die pictures
Post by: magic on March 03, 2022, 04:23:36 pm
Jung defines CMRR as the ratio of differential gain to common mode gain (or vice-versa, if you want negative decibels). Open loop differential gain behaves as we know, but common mode gain may vary with frequency too and in all sorts of weird ways (in practice: it probably increases, because capacitances start to play role, in theory: opposite effects could cancel out at some frequencies). So the CMRR curve needs not be straight.

The circuit for the input current cancelaton also helps a lot with CMRR, as it includes a kind of cascode for the input transistors. The LT1001 seems to use one more stage here. Some difference could also be from the biasing current source here.
OP07 also has two cascode stages above the input transistors. Base current of the lower cascode is mirrored into the base of the input transistor, exactly as shown on LT1001 schematic. Same guy, same tricks ;)

Old TI OP07 datasheets contain a complete schematic which shows those details, but it's super-ugly like everything from TI and there are some errors in the output stage - it wouldn't work as drawn. Current TI datasheet contains a 741 schematic.

You are correct about input stage biasing - OP400 current source is cascoded, OP07 is not. That's a more plausible explanation than some input stage gain woo-woo ::)

In the frequency domain the higher DC gain is visible only at very low frequency, but when looking in the time domain it still makes a difference after relatively short time (e.g. sub ms range).
That's also true, I just keep forgetting about it :palm:
The effect shows up in AC as well. Two ideal opamps simulated below, both maintain their DC gain accuracy to 10Hz, far above their dominant poles (1Hz, 0.1Hz).
"OP77" exceeds "OP07" DC~10Hz gain accuracy up to 40Hz.
Title: Re: Opamps - Die pictures
Post by: Noopy on March 05, 2022, 09:12:59 pm
(https://www.richis-lab.de/images/Opamp/47x01.jpg)

RCA CA741, another µA741 variant.


(https://www.richis-lab.de/images/Opamp/47x02.jpg)

The CA741 looks similar to the schematic shown in the LM741 datasheet (that doesn´t show the circuit used in the LM741).

R4 and R11 have different values and there is the additional diode D4. Looks like it does some additional current limiting in the lowside path.


(https://www.richis-lab.de/images/Opamp/47x03.jpg)

Yeah, there was a problem in the circuit. The bondwire conducting the negative supply is molten...  :o


(https://www.richis-lab.de/images/Opamp/47x05.jpg)

(https://www.richis-lab.de/images/Opamp/47x04.jpg)

The die is 1,6mm x 1,4mm. 6029A is a typical RCA naming.

Here we can see that the non inverting input is damaged too.


(https://www.richis-lab.de/images/Opamp/47x15.jpg)

In the datasheet there is a picture of the metal layer.


(https://www.richis-lab.de/images/Opamp/47x06.jpg)

(https://www.richis-lab.de/images/Opamp/47x07.jpg)

(https://www.richis-lab.de/images/Opamp/47x08.jpg)

The bondwire of the negative supply had to conduct a lot of current. It´s molten away and there is a shallow crater. You can see some metal splatter around the bondpad.

There is another disruption a little above the bondpad.


(https://www.richis-lab.de/images/Opamp/47x09.jpg)

(https://www.richis-lab.de/images/Opamp/47x10.jpg)

The non inverting input is severely destroyed too. There is a offset wire near the input wire that is molten away too.


(https://www.richis-lab.de/images/Opamp/47x11.jpg)

I assume there was a positive potential at the negative supply of the CA741. There was no overcurrent in the output stage. Q17 collector is cut but it looks like a secondary damage.

R11 is a low impedance path into the circuit. In this case Q14 base-collector conducts the current, same with Q4. Q3 base-emitter and Q1 emitter-base break down at relatively low voltages and you are at the non inverting input.

In this case R11 dissipates a lot of power which corresponds to the damage in this place. The non inverting input wire is very thin and fuses proportionaly fast. It´s interesting that Q1 and Q3 look like they survived the current in breakdown mode.


(https://www.richis-lab.de/images/Opamp/47x14.jpg)

R4 and R5 can be adjusted by the metal layer. You can adjust the current in the differential input stage and in the voltage amplifier stage.


(https://www.richis-lab.de/images/Opamp/47x12.jpg)

Besides the CA741 in the datasheet there is a CA748 without a compensation capacitor. The offset compensation pins are moved above the current mirror so you can use one of them to connect the capacitor. In the CA748 pin 8 is used to connect the second electrode of the compensation capacitor.


(https://www.richis-lab.de/images/Opamp/47x13.jpg)

In the datasheet you can find the metal layer of the CA748 too.  :-+


https://www.richis-lab.de/Opamp45.htm (https://www.richis-lab.de/Opamp45.htm)

 :-+
Title: Re: Opamps - Die pictures
Post by: magic on March 06, 2022, 05:47:53 pm
Hi Noopy, base-emitter breakdown of the input stage is not necessary to send reverse current to the input pin. The substrate is connected to V- and there is a diode from the substrate to every NPN collector and every PNP base. If you connect a positive voltage to V-, there is plenty of opportunity for current to flow to multiple other pins. This could be the reason why the negative bond wire was the first one to melt.

edit
Eh, no, it makes no sense. Just getting to Q1 collector isn't enough, because Q1 BC junction would be reverse biased then.

Other than that, the schematic is wrong as usual with 741.
Q15 collector is VCC, there is a PNP emitter follower between the VAS and the output stage, the PNP output has active current limiting. I doubt that we will ever see an IC which matches this schematic originally published by Fairchild...
Title: Re: Opamps - Die pictures
Post by: Noopy on March 06, 2022, 06:39:48 pm
I totally ignored the substrate. Of course positive potential at V- will drive some current through the substrate. There is a significant resistance too. Probably the circuit and the substrate share the current flowing from V- to the non inverting input. Still breakdown of Q1 and Q3 is necessary.  :-+

I didn't take a closer look at the output stage. You are right, another schematic not fitting to the circuit.

Title: Re: Opamps - Die pictures
Post by: David Hess on March 06, 2022, 11:12:57 pm
AC CMRR usually does not depend much on the open loop gain. Much is related to the GBW and how the compensation is done. The curves in the OP400 data-sheet look a bit odd and not really consistent: the AC CMRR is somewhat curved and would suggest deviation from simple dominant pole compensation, while the open loop gain / phase looks like simple ideal dominant pole compensation.

A lot of data sheets of that era showed the wrong CMRR and PSRR curves because they were measured wrong and showed the open loop gain instead.

Quote
The circuit for the input current cancelaton also helps a lot with CMRR, as it includes a kind of cascode for the input transistors. The LT1001 seems to use one more stage here. Some difference could also be from the biasing current source here.

I do not know the timing, but George Erdi might have fixed the input bias current cancellation circuit after reports of it causing problems with CMRR in the OP-27.  One of the claims to fame of the Linear Technology designs was solving this issue.

Quote
The open loop gain can be a tricky part in the specs, as there is also ouput stage cross over. So the gain is not constant, but can change depending on the operation point.

One of the complaints about the OP-07 which was suppose to have been solved in improved replacements is its excessively nonlinear gain with operating point.
Title: Re: Opamps - Die pictures
Post by: Noopy on March 09, 2022, 04:50:23 am
I have done an update on the CA741:


(https://www.richis-lab.de/images/Opamp/47x17.jpg)

(https://www.richis-lab.de/images/Opamp/47x16.jpg)

In my view the schematic looks like this.


(https://www.richis-lab.de/images/Opamp/47x18.jpg)

And here we have the updated path of destruction.


https://www.richis-lab.de/Opamp45.htm (https://www.richis-lab.de/Opamp45.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on March 09, 2022, 07:46:47 am
LTspice rules ;D

But you missed R3 on the schematic and I'm not sure if I like those current mirrors drawn as diodes - I draw them as transistors so it's clear that there is the same kind of transistor on the input and the output of the mirror.

Another issue is D5. Its structure is the same as BE junction of a PNP and the dimensions of the surrounding isolation are similar to PNP collector - I suspect that a fair amount of minority carriers are injected into the cathode and collected by isolation, making this device a PNP emitter follower with grounded collector. For a true PNP diode there should be a collector which catches those minority carriers and delivers them to the base through a metal short. Identical two transistor VAS circuit with a "true" diode attached below for reference (your AD588 opamp). The difference is of course not major, the circuit still functions the same.

edit
Look at Q23 on page 11 of this PDF (http://www.ee.bgu.ac.il/~angcirc/History/Solutions_2003_2004_B/SomeStuff/History18opamp.pdf).
For all those years, this is the only guy who really got it.
At least out of those who published materials about 741.

Other than that, yes, this seems to be the basic µA741 schematic. It's identical to the AD741 schematic produced by Ken Shirriff (https://www.righto.com/2015/10/inside-ubiquitous-741-op-amp-circuits.html). This chip appears identical to the SGS 741 you posted recently - even physical layout of components is almost the same. And the SGS is practically identical, including layout, to Fairchild and AMD µA741 shown by Andrew Resnick (https://resnicklab.wordpress.com/2013/05/14/meanwhile/). And these were metal can devices (no signs of acid damage - look at other chips from that guy) made in 1971 and 72 - the first four years of production. This is probably as close to the original 741 designed by David Fullagar as it gets.

Later modifications include:
- transplanted LM101A input stage - this may have been National's job
- using the input stage mirror for sink current limiting instead of D6,Q14
- some cascoding of Q10 collectors
- different physical layouts

Now we can take a moment to laugh at all the people who believed the dumbed down schematic published by Fairchild ;D
Like Wikipedia editors and numerous university professors who produced "analyses" of a circuit which most likely never existed and missed the absence of sink current limiting.
Or the designers of this discrete 741 kit (https://shop.evilmadscientist.com/productsmenu/762). Their datasheet silently omits "short circuit: unlimited" in absolute maximum ratings - what could be the reason? >:D
Title: Re: Opamps - Die pictures
Post by: Noopy on March 09, 2022, 10:19:59 am
LTspice rules ;D

LTspice and PowerPoint.  ;D


But you missed R3 on the schematic and I'm not sure if I like those current mirrors drawn as diodes - I draw them as transistors so it's clear that there is the same kind of transistor on the input and the output of the mirror.

You are right. And there were two Q18. Done!  :-+
I don´t like the current mirrors with the diodes but I wanted to stay near the schematic of the datasheet.


Another issue is D5. Its structure is the same as BE junction of a PNP and the dimensions of the surrounding isolation are similar to PNP collector - I suspect that a fair amount of minority carriers are injected into the cathode and collected by isolation, making this device a PNP emitter follower with grounded collector. For a true PNP diode there should be a collector which catches those minority carriers and delivers them to the base through a metal short. Identical two transistor VAS circuit with a "true" diode attached below for reference (your AD588 opamp). The difference is of course not major, the circuit still functions the same.

That´s an interesting point, thanks!
I will leave the diode in the schematic but I have added a hint:


(https://www.richis-lab.de/images/Opamp/47x19.jpg)


Now we can take a moment to laugh at all the people who believed the dumbed down schematic published by Fairchild ;D
Like Wikipedia editors and numerous university professors who produced "analyses" of a circuit which most likely never existed and missed the absence of sink current limiting.
Or the designers of this discrete 741 kit (https://shop.evilmadscientist.com/productsmenu/762). Their datasheet silently omits "short circuit: unlimited" in absolute maximum ratings - what could be the reason? >:D

 ;D
Title: Re: Opamps - Die pictures
Post by: Noopy on March 13, 2022, 07:31:16 am
(https://www.richis-lab.de/images/Opamp/48x01.jpg)

(https://www.richis-lab.de/images/Opamp/48x03.jpg)

One more analog AMD circuit, the AM211, similar to the µA211 or the LM211. The AM211 is a better grade than the AM311 which gives you a bigger operating temperature range. There is also a AM111.

That´s a nice old ceramic package!  8)


(https://www.richis-lab.de/images/Opamp/48x02.jpg)

(https://www.richis-lab.de/images/Opamp/48x04.jpg)

On top of the package there are two metal sheets soldered together. Some heat and you can open the AM211.


(https://www.richis-lab.de/images/Opamp/48x05.jpg)

(https://www.richis-lab.de/images/Opamp/48x06.jpg)

The pins were molded into the ceramic.


(https://www.richis-lab.de/images/Opamp/48x07.jpg)

(https://www.richis-lab.de/images/Opamp/48x08.jpg)

Hey that´s exactly the same circuit as in the Fairchild µA311 (https://www.richis-lab.de/Opamp43.htm (https://www.richis-lab.de/Opamp43.htm)). The parts are just a little different and we have the AMD logo at the lower edge.


https://www.richis-lab.de/Opamp46.htm (https://www.richis-lab.de/Opamp46.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on March 21, 2022, 07:52:56 am
Did somebody say "pictures" rather than "photographs"?
Here's one :P >:D

Well, reason is because I wondered if old Burr-Brown Difet opamps like OPA111, OPA128, OPA2111, OPA2107 used a complementary bipolar process like OPA627 or perhaps something simpler. Their mediocre bandwidth speaks in favor of "something simpler", and another reason is that Burr-Brown was so much obsessed with using JFET cascodes rather than BJT and making them cost-effective with tricks. The rationale they quote in OPA111 datasheet and related patent (US4550291) is base current noise of BJTs, but five years later they released OPA627 with very good overall noise performance and BJT cascodes. Hmm...

There is a small problem: most of those early Difet chips (including the classic 111/2111) are discontinued and you wouldn't want to know the prices of those that aren't. However, there are pictures of the metal layer in old Burr-Brown databooks. Could that be enough? :-/O


This is OPA2107, perhaps the simplest of those opamps. With a little coloring, I think I can figure it out.

The inputs (red/blue) go to the gates of eight P-JFETs in usual common centroid layout.
The sources (pale red/blue) go to degeneration resistors (laser trimmed for offset) and a common current source (pale pink).
The drains (orange/violet) go to bootstraped P-JFET cascodes (without tricks this time) and emerge on the other side (yellow/pink).
These signals meet at what looks like a classic NPN current mirror with emitter degeneration (laser trimmed for drift, one side goes to NC pin). The bases (magenta) are driven by an emitter follower from the inverting side, on the noninverting side identical emitter follower drives the VAS (light green).
Both followers are loaded by NPN sinks driven from the core bias generator at the top (burgundy). Emitter resistors are clearly visible.
Another, larger sink loads the cascode gate bootstrap circuit (brown) and serves as a reference for the input stage current generator.
The current generator appears to be a lateral PNP Wilson current mirror. This is damning evidence, showing that the process is noncomplementary as suspected.
The VAS is loaded (green) with another lateral PNP near the core bias generator and drives an NPN emitter follower going to the output through some resistor (cyan), there is active current limiting by another small NPN.
Not sure how output sinking works, it should be that big grey stuff in the center :-//

A closeup of the Wilson mirror. This looks blatantly like lateral PNPs with emitter degeneration and 1:3 current ratio. It surely doesn't look like vertical PNPs found in OPA627 and doesn't look like JFETs either.
(https://www.eevblog.com/forum/projects/opamps-die-pictures/?action=dlattach;attach=1444789;image)

And mostly complete schematic. Much simpler than OPA627, more like TL072 on steroids :D
(https://www.eevblog.com/forum/projects/opamps-die-pictures/?action=dlattach;attach=1444795;image)
Title: Re: Opamps - Die pictures
Post by: Noopy on March 21, 2022, 04:22:27 pm
Well done!  :-+

Will have to take a look into a OPA111 and/or his brothers...  :-/O :)
Title: Re: Opamps - Die pictures
Post by: David Hess on March 21, 2022, 07:36:27 pm
It reminds me of a 741/301 input stage with the NPN and PNP input transistors replaced with JFETs.
Title: Re: Opamps - Die pictures
Post by: magic on March 21, 2022, 10:43:16 pm
Will have to take a look into a OPA111 and/or his brothers...  :-/O :)
Beware that these are audioph00l parts so there is a lot of fakes around.
I have one OPA2111 from auction site - kinda works, but much noisier. Probably some TL071, LF411, LF356, ...

I have this picture from the cover of a different databook. Not sure what it is, but it looks very similar to 111 and 128 drawings in the 1995 databook.

In these chips the input stage is again a cascoded JFET pair, but it's loaded with resistors to ground like OP07 upside down. The second stage starts with JFET source followers (there is one extra on the inverting side :wtf:) and that's where I'm lost...
Title: Re: Opamps - Die pictures
Post by: Noopy on March 21, 2022, 11:02:45 pm
Will have to take a look into a OPA111 and/or his brothers...  :-/O :)
Beware that these are audioph00l parts so there is a lot of fakes around.

Most people would get angry buying a fake part. I'm just curious about the content. For now I ordered the cheapest OPA111 I could get on eBay.  ;D It will take some time...
Title: Re: Opamps - Die pictures
Post by: TiN on March 22, 2022, 05:10:12 am
AM211 is just pure joy and tears to my eyes.  :-+
Title: Re: Opamps - Die pictures
Post by: magic on March 27, 2022, 02:17:24 pm
A little more madness :o

I'm not 100% sure, but this is the most sense I can make out of those images.
I wouldn't even get that far, if not for availability of four slightly different variants of the same basic curcuit: the two channels of OPA2111, OPA111 (pictured) and OPA128.

The PNPs are all lateral. The 1st and 3rd stage current sources are cascoded with JFETs. Input stage current appears to be further amplified by an NPN Wilson mirror. Q32 bootstraps the input stage cascodes, I'm not entirely sure what D6 is doing and if it even exists at all or what else could be there if not a diode.

J3,J4 are the input pair's cascodes, their current is amplified by NPN mirrors. This is the patented "noise free cascode" advertised on the first page of the datasheet. The trick is that the JFETs can be made smaller, but the circuit is still very accurate - all current entering at the top exits at the bottom, no noise current is added or subtracted despite the use of BJTs.

It appears that they were really serious about avoiding BJTs near the input stage, because the signal generated on R3,R4 is then picked up by JFET source followers. In the second stage, Q9 regulates J5,Q5 current to equal Q7 current. Any difference between J6,Q6 and Q8 currents is fed to the next stage.

The third stage is a two transistor VAS with an emitter follower Q15 at the output. J7 helps equalize collector voltages of Q5/Q7 and Q6/Q8. It may also be providing signal feedforward around the second stage straight to the VAS collector node through common base Q13, but then again, C1 may be preventing it. Not sure how all that compensation is set up here. I'm not even 100% sure if I got all capacitor connections right, but that's what they seem to be.

The output stage consists of emitter follower Q18 and a JFET/bipolar opamp-inside-opamp for sinking. A bit like LF156, but different.

Overall, crazy stuff :scared:

edit
schematic correction near Q28 ::)
Title: Re: Opamps - Die pictures
Post by: Kleinstein on March 27, 2022, 03:33:50 pm
It may not be the noise that they don't like with PNPs.  Lateral PNPs would also be relatively poor PNPs with low gain and thus relatively high current noise at the base.  It could also be the speed that can be better with P-JFETs compared to lateral PNPs. If you already have the process for the FETs, why not use them also for the cascode and 2nd stage.
Title: Re: Opamps - Die pictures
Post by: magic on March 27, 2022, 06:56:43 pm
Cascoding of current sources makes sense as it should improve output impedance and bandwidth; LF156 did it too.

The second stage is less obvious, because NPNs could be used here in theory and those JFETs take more space than OP07 or OP27 input pair. What isn't clear is whether an ordinary NPN differential pair would permit a three stage topology in some manner - common three stage opamps from the era used PNP second stage which naturally feeds an ordinary NPN VAS, while OPA111 employs that weird arrangement with common base NPNs driven by JFETs which likely couldn't be replaced by PNPs.

OPA111 appears to benefit from its three stage architecture with high guaranteed gain (120dB) and CMR/PSR better than two stage designs like TL072 or LF156, including BB's improved derivatives such as OPA156, OPA2107, OPA606.


Regarding noise, this was said in the datasheet:
Quote
Extremely low noise is achieved with patented circuit design techniques. A new cascode design allows high precision input specifications and reduced susceptibility to flicker noise.
and AD's applications handbook by Jung:
Quote
The OPA111 circuit employed P-channel JFETs in the input and second stages, and a first stage cascode design for low bias current variation with input CM changes. The design addressed some of the weak points of the previous LF155/156/157 series (Reference 39, again). Reference 49 cited several LF15x circuit weaknesses; one was the use of current source loading for the input JFET pair, another was the means of offset trimming, and another was potential susceptibility to popcorn noise, due to the noise currents of the second stage bipolar differential pair. These points were addressed by the OPA111 design.

Reference 49 is Steve Millaway, "Monolithic Op Amp Hits Trio of Lows," Electronic Design, February 9, 1984, which I wasn't able to locate even after signing up to ED's website.
Title: Re: Opamps - Die pictures
Post by: Noopy on April 03, 2022, 03:39:47 am
(https://www.richis-lab.de/images/Opamp/49x01.jpg)

Another µA709 variant, a TL1709 built by Telefunken. The TL1709C is the consumer part.


(https://www.richis-lab.de/images/Opamp/49x06.jpg)

The datasheet looks familiar.


(https://www.richis-lab.de/images/Opamp/49x02.jpg)

(https://www.richis-lab.de/images/Opamp/49x03.jpg)

The design of the die looks familiar too but it seems to be a proprietary development.


(https://www.richis-lab.de/images/Opamp/49x04.jpg)

(https://www.richis-lab.de/images/Opamp/49x05.jpg)

The test transistor is strange... What are the purple areas doing?  :-//


https://www.richis-lab.de/Opamp47.htm (https://www.richis-lab.de/Opamp47.htm)

 :-/O



I somehow lost track of the circuit. Let´s fetch the schematic of the LM709 because there are designators:


(https://www.richis-lab.de/images/Opamp/21x03.jpg)

What was the job of Q7?  :-//
@magic?  ;)
Title: Re: Opamps - Die pictures
Post by: T3sl4co1l on April 03, 2022, 04:44:45 am
Is that kinda like a Vbe multiplier, between Q8/Q9 bases?  Looks weird because it just happens to also be the diff pair biasing?

Next thought: Q15 and Q4/Q6 act like a current mirror, balancing the current in R1/R2 with R5/R6... making sort of a current source or something?

It's also tied in with main bias (~Q10), which isn't going to be very stable, but varies with signal level.  Or maybe that's been balanced too.

These old, highly optimized (tightly coupled) ICs are always something of a puzzle to tease out. :)

Tim
Title: Re: Opamps - Die pictures
Post by: magic on April 03, 2022, 09:01:01 am
This Telefunken schematic is hundred times more logical than Widlar's mess.

OK, let's go. We apply power, all transistors are off, the 10kΩ start to conduct. Second stage output emitter followers turn on, the left one pulls up input stage collector loads. The second stage turns on and supplies power to the bias generator (approximately 3.6kΩ||10kΩ + 18kΩ), a fraction of that current is mirrored by the Widlar current source into the input pair and drops some smaller voltage across 25kΩ. This pulls down on second stage bases, stabilizing the second stage common mode level.

I suppose most of the supply voltage is dropped across the bias generator (~21kΩ), four times less is dropped across the two 10kΩ resistors (they are paralleled as far as bias is concerned) and emitter-collector voltage of the second stage is perhaps a (low) few volts, determined by three diode drops plus 25kΩ voltage (which is a certain ratio of 21kΩ voltage). All nice and stable (ignoring supply variations) and input common mode swing is entirely absorbed by input stage collectors.

3kΩ resistors and the NPN diode bias the Darlington pairs of the second stage: a small current exiting the driver through 3kΩ is enough to turn on the inner transistor much harder so it conducts most of the pair's current.

Differential voltage across 25kΩ produced by the first stage is amplified at the 10kΩ resistors by the second stage. The right side goes straight to an NPN emitter follower. The left side goes to a different NPN emitter follower which slightly shifts common mode point of the second stage and thus drives a PNP emitter follower hanging off the second stage emitters. The difference between the complementary emitter followers determines 1kΩ resistor current, which is passed to the third stage by the PNP.

Resistors in the third stage need to be calculated so as to produce the right current in 1kΩ when the second stage is in balance. Knowing Widlar, they likely are, but checking this would require calculating the input stage current source's behavior. I'm too lazy/clueless, so if I really had to do it, I would just load the circuit into SPICE. The third stage itself is a fairly simple common emitter NPN loaded with 20kΩ which drives a pair of complementary emitter followers in class B. The 30kΩ appears to implement some local negative feedback in this stage.

edit
We should perhaps consider that NPN,1kΩ,PNP,10kΩ stack to be the third stage as it works outside the second stage and VAS local compensation loops and clearly has some voltage gain of its own: 10x ignoring base impedance of the VAS, but VAS rE is 26mV/0.7mA = 37Ω so its input impedance ought to be β times more or a few kΩ. So actual gain of this stage is maybe 3~5x. Then the VAS is the fourth stage.
Title: Re: Opamps - Die pictures
Post by: Noopy on April 03, 2022, 05:30:28 pm
These old, highly optimized (tightly coupled) ICs are always something of a puzzle to tease out. :)

I totally agree with you!
These people were genius getting the most out of a few non ideal parts.  :clap:


...

Thanks!  :-+
Title: Re: Opamps - Die pictures
Post by: MegaVolt on April 04, 2022, 08:41:14 am
What is a round area? I have seen something similar only on buried zener diodes.
Title: Re: Opamps - Die pictures
Post by: Noopy on April 04, 2022, 08:47:44 am
That´s a PNP transistor. Nothing too special.

Here for example in a Raytheon LM318:

(https://www.richis-lab.de/images/Opamp/05x02.jpg)

Sometimes they are oval.
Title: Re: Opamps - Die pictures
Post by: Noopy on April 13, 2022, 10:19:58 am
(https://www.richis-lab.de/images/Opamp/50x01.jpg)

LA741, one more µA741 variant. There is no manufacturer logo and I found no datasheet but with the "LA" I assume it was built by Sanyo.


(https://www.richis-lab.de/images/Opamp/50x02.jpg)

Here the negative supply is connected directly to the case.


(https://www.richis-lab.de/images/Opamp/50x03.jpg)

The die looks pretty similar to the RCA CA741 (https://www.richis-lab.de/Opamp45.htm (https://www.richis-lab.de/Opamp45.htm)).


(https://www.richis-lab.de/images/Opamp/47x16.jpg)

The schematic of the CA741 applies to the LA741 too. There is just one resistor missing on the die: R13.


(https://www.richis-lab.de/images/Opamp/50x04.jpg)

R4 (bias current input stage) can be changed by modifying the metal layer.

In the right part of the picture there is a small unconnected resistor. It looks like it belongs to R11 but perhaps it is an option to get  R13 into the system.


(https://www.richis-lab.de/images/Opamp/50x05.jpg)

It looks like the die got a little hot at the output bondpad.  :o


https://www.richis-lab.de/Opamp48.htm (https://www.richis-lab.de/Opamp48.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on April 13, 2022, 03:52:17 pm
R13 was a pinch resistor on implementations that had it so the unused one seems related to R11.

This looks like a perfect copy of Fairchild. The only difference I see is lack of the "A" mark under the unused transistor at the top, but even that square/circle mark between the input pads is preserved.
Title: Re: Opamps - Die pictures
Post by: Noopy on April 13, 2022, 07:04:48 pm
You are right, in both points.  :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on May 13, 2022, 07:09:52 pm
(https://www.richis-lab.de/images/Opamp/51x02.jpg)

(https://www.richis-lab.de/images/Opamp/51x01.jpg)

floobydust had two OPA627 which puzzled him. He thought they could be fake parts.

The markings are very hard to reed.


(https://www.richis-lab.de/images/Opamp/51x03.jpg)

(https://www.richis-lab.de/images/Opamp/51x04.jpg)

Not fake part!  :-+
Now we have better pictures of the OPA627!  8)
Of course we can´t be sure if they are recycled or scrapped parts...  :-//


(https://www.richis-lab.de/images/Opamp/51x05.jpg)

Mask revisions are the same as in the "old" OPA627.


(https://www.richis-lab.de/images/opamp/23x04.jpg)

(https://www.richis-lab.de/images/Opamp/51x06.jpg)

Yeah, my pictures are getting better.  8)


(https://www.richis-lab.de/images/Opamp/51x07.jpg)

As with many other Burr-Brown parts that are laser trimmed, there are non-functional squares on the edges that have been partially cut. A letter is assigned to every square. For the ISO120 (https://www.richis-lab.de/iso01.htm (https://www.richis-lab.de/iso01.htm)) these are A to T. For the OPA541 (https://www.richis-lab.de/Opamp02.htm (https://www.richis-lab.de/Opamp02.htm)) and the VFC110 (https://www.richis-lab.de/vfc01.htm (https://www.richis-lab.de/vfc01.htm)) A to H was enough. In the OPA627 squares from A to W were integrated.


(https://www.richis-lab.de/images/Opamp/51x08.jpg)

One of the p-channel J-FETs at the inputs.


(https://www.richis-lab.de/images/Opamp/51x13.jpg)

In the Analog Applications Journal (SLYT595) Texas Instruments shows what is meant by dielectric isolation. On the left you see an ordinary J-FET. The transistor is isolated from the substrate by the pn junction formed at the interface. The signal source is loaded with the capacitance Cgss. This is often problematic for high impedance sources. In addition, the capacitance varies with the input voltage, which creates distortion.

If one wants to reduce the parasitic capacitances of the transistors, one can insert an insulating silicon oxide layer between the transistors and the substrate. This layer reduces the capacitance Cgss and ensures that the residual capacitance remains constant regardless of the input voltage. As described with the first OPA627 (https://www.eevblog.com/forum/projects/opamps-die-pictures/msg3317812/?topicseen#msg3317812 (https://www.eevblog.com/forum/projects/opamps-die-pictures/msg3317812/?topicseen#msg3317812)), however, the manufacturing process is much more complex.


(https://www.richis-lab.de/images/Opamp/51x09.jpg)

You can roughly guess the structure of the transistors. The yellowish areas are contacted by the gate potential. The drain and source lines have different widths above the transistors. But they both seem to contact a deeper layer through cutouts. Most likely this is the p-doped channel.

The blue area is then n-doped and represents the upper part of the gate. The yellowish areas are thus likely to be highly n-doped areas. The high n-doping is necessary to provide an ohmic contact with the metal layer and to avoid a Schottky contact. It also ensures a low resistance distribution of the gate potential. The gate line additionally contacts greenish areas at the upper and lower edges of the transistor. I assume that this is the lower gate electrode.


(https://www.richis-lab.de/images/Opamp/51x12.jpg)

In the left image, the metal layer was removed (3min HF, 3min HCL, 15min HF). Now you can guess the drain and source contacts.

In the right image more silicon oxide was dissolved (25min HF). In the active area there are now almost no colored areas left. This indicates that the silicon level has been reached. The different colors arise just in the thin silicon oxide layers where light resonances occur.


(https://www.richis-lab.de/images/Opamp/51x14.jpg)

It is interesting that the frame structure still appears colored. After the silicon oxide layers have been removed, the isolation regions usually remain colorless, since they are merely inverse dopants within the substrate (see https://www.richis-lab.de/Howto_Decap_HF.htm (https://www.richis-lab.de/Howto_Decap_HF.htm) for example). In case of the OPA627 with its dielectric isolation of the transistors, the isolation regions are deeper silicon oxide layers which have not yet been dissolved and accordingly still exhibit a slight colorfulness.


(https://www.richis-lab.de/images/Opamp/51x10.jpg)

(https://www.richis-lab.de/images/Opamp/51x11.jpg)

The die has suffered some damage at one edge. As described in the first OPA627 post, dielectric isolation is created by grinding a suitably prepared wafer and then bonding it to another wafer rotated by 180°. Here it seems like exactly this upper part broke off.


https://www.richis-lab.de/Opamp22.htm#OPA627x2 (https://www.richis-lab.de/Opamp22.htm#OPA627x2)

 :-/O
Title: Re: Opamps - Die pictures
Post by: floobydust on May 13, 2022, 09:52:39 pm
What had me stumped thinking it's a fake is those particular OPA627 behaved different and measured different than ones from Digi-Key, and different from OPA828, AD744 as well.
I found different resistance values and a couple substrate? diodes, where there should have been none. The parts are also not stable around unity-gain where the DK parts are fine. Same Icc.

So it looks like they are manufacturing rejects?

[attachimg=2]
Title: Re: Opamps - Die pictures
Post by: T3sl4co1l on May 14, 2022, 03:34:46 am
Neato, so if you leave it soaking in HF, do the transistors fall off? :D

Tim
Title: Re: Opamps - Die pictures
Post by: magic on May 14, 2022, 09:28:12 am
You swapped sources and drains, as usual ;D
Title: Re: Opamps - Die pictures
Post by: Noopy on May 14, 2022, 09:41:05 am
So it looks like they are manufacturing rejects?

That´s possible...
I´m afraid that happens quite often. Unfortunately such parts don´t catch one´s eye immediately.  :-BROKE


Neato, so if you leave it soaking in HF, do the transistors fall off? :D

Ething for a day or two supplies you with a lot of nice J-FETs for your circuits.  ;D


You swapped sources and drains, as usual ;D

Just to check if you are still attentive.  ;D
Thanks!  :-+
Title: Re: Opamps - Die pictures
Post by: Kleinstein on May 14, 2022, 11:38:09 am
The difference in resistance is not that large. That should be well within the normal variations for the silicon resistors.
I doubt that AD would release rejects. It would be more likely to have recycled parts that may have got some initial ESD or thermal damage.
Title: Re: Opamps - Die pictures
Post by: Noopy on May 14, 2022, 11:48:19 am
I doubt that AD would release rejects.

I agree with you, AD won't release rejected parts but perhaps there is someone around emptying the bins and putting the scrapped parts into the market.
It seems like that happens every now and again: https://www.richis-lab.de/REF06.htm (https://www.richis-lab.de/REF06.htm)
Title: Re: Opamps - Die pictures
Post by: Noopy on June 02, 2022, 07:06:13 pm
(https://www.richis-lab.de/images/Opamp/52x01.jpg)

The company George A. Philbrick Researches designed the first commercially available operational amplifier in 1953. It was built with two tubes. Later Teledyne acquired Philbrick.

The 1322 is one of a series of op-amps referred to as "optimized 741's". The 1321 and 1322 share one datasheet that describes them as "High Slew Rate Operational Amplifier". The slew rate of the 1322 is typically 80V/µs. The 1321 is much slower at 20V/µs. The bandwidth of the 1322 is up to 20MHz, while the 1321 gives you up to 120MHz. If you want to achieve high output levels you should use the 1322. For a high bandwidth the 1321 is to be preferred.

Up to a gain of 10 the opamp is stable. Below that the bandwidth has to be limited with a capacitor at pin 8. Pin 8 is very sensitive. If one wants to achieve the maximum bandwidth the datasheet recommends cutting the pin near the package to keep the parasitic capacitance low.

The bias current of the 1322 is typically 100nA, which is a low value for this category of opamp. The supply voltage may be between +/-8V and +/-20V. The 1972 Teledyne Philbrick catalog states a price of $20. Today (2022) this corresponds to a value of 140$.


(https://www.richis-lab.de/images/Opamp/52x02.jpg)

In the overview you can already see that the bonding process was problematic. Failed bonds have left residues on the connection pins.


(https://www.richis-lab.de/images/Opamp/52x03.jpg)

The dimensions of the dies are 1.6mm x 1.2mm. Remnants of failed bonds can be seen on the bondpads.

The symmetrically constructed input stage extends centrally from the left edge to the right edge. The output stage can be found at the lower edge, especially in the left area. Above the bondpad V+ there is a tiny capacitor which apparently represents a minimum limitation of the bandwidth as long as no additional capacitor is connected externally.

In the upper left corner are two lonely resistors. The current sink of the input stage is integrated in this area too. Probably in the 1321 these resistors are used to reduce the current of the current sink. That would reduce the slew rate too. And it would fit to the fact that the bias current of the 1321 is lower by a factor of 20 compared to the 1322.


https://www.richis-lab.de/Opamp49.htm (https://www.richis-lab.de/Opamp49.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on June 03, 2022, 09:10:25 am
It looks so "optimized" that it doesn't even resemble a 741.

I can't find the datasheet, is 120MHz the bandwidth or the gain-bandwidth product at 10x gain?
Not exactly the same ;)
Title: Re: Opamps - Die pictures
Post by: Noopy on June 03, 2022, 09:27:20 am
For example:
http://www.philbrickarchive.org/1972%20product%20guide.pdf (http://www.philbrickarchive.org/1972%20product%20guide.pdf)

Page 16/17:
"Small signal (unity gain, open loop), min" and "100MHz"
but hey, there is a small 2 at the 1321 stating "G x BW at A=3". :palm:

You are right.  :-+


I don´t see much 741 either.  ;D
Title: Re: Opamps - Die pictures
Post by: David Hess on June 04, 2022, 08:54:25 am
It looks so "optimized" that it doesn't even resemble a 741.

It is too bad Teledyne was so parsimonious with their datasheets but even so, it is obviously not a 741 based design; it has input bias current cancellation and the maximum differential input voltage is 12 volts.  Performance and the 12 volt differential voltage limit make it similar to a Signets 531 which has a Darlington NPN only input stage.

I do not see any mention of the 741 in the 1321/1322 datasheets but the 1332 datasheet does make a comparison to the 741 because its offset nulling configuration and unity-gain stability make it a drop in replacement.
Title: Re: Opamps - Die pictures
Post by: magic on June 04, 2022, 09:22:32 am
There is no bias cancellation but emitter follower drivers (loaded with active sinks) in front of a heavily degenerated differential pair. That's how they got low bias and high impedance (i.e. low variation of bias with input voltage) with fast slew rate. The input stage is quite obvious.

The rest I think is a folded cascode voltage gain stage and emitter follower output (think AD829 et al) fabricated in complementary bipolar technology on dielectric isolation, like OPA627, except no JFETs and made in 1972 :o

I will have to take a closer look later.
Title: Re: Opamps - Die pictures
Post by: David Hess on June 04, 2022, 07:52:31 pm
There is no bias cancellation but emitter follower drivers (loaded with active sinks) in front of a heavily degenerated differential pair. That's how they got low bias and high impedance (i.e. low variation of bias with input voltage) with fast slew rate. The input stage is quite obvious.

I was going by the datasheet which lists bipolar input bias current and identical input offset current for the 1321.

Quote
The rest I think is a folded cascode voltage gain stage and emitter follower output (think AD829 et al) fabricated in complementary bipolar technology on dielectric isolation, like OPA627, except no JFETs and made in 1972 :o

I wondered if it might be a dielectric isolated process.  That plus transconductance reduction would explain the higher performance.
Title: Re: Opamps - Die pictures
Post by: magic on June 05, 2022, 06:38:41 am
I wondered if it might be a dielectric isolated process.
Everything points to that. Isolation islands look very much like those on OPA627. And it has to be complementary because there are transistors that need to be PNPs for the circuit to work which don't look like the usual lateral PNPs and apparently work just fine at 20MHz.

One such process that's known to have existed in the '70s was owned by Harris and bingo, this chip appears to be rebadged HA-2520. It's a lot more complex than textbook examples or Analog's simplified schematics, but if you look closely Q24,Q23 are the current mirror, driven by Q25,Q20 emitter followers, passing its current through Q25,Q13 common base to the summing node at Q12 base, which drives the diamond buffer Q14~Q19 (no idea what's the point of the diodes Q14 level-shifts Q11 base to prevent Q12 saturation and Q18 restores proper output bias, but why is Q14 not placed above Q16 base instead?). The compensation cap at Q12 base is missing on this schematic.

(https://www.eevblog.com/forum/projects/opamps-die-pictures/?action=dlattach;attach=1503628;image)

Harris 1977 linear databook contains an illustration of the dielectric isolation process and their vertical PNP structure.
Title: Re: Opamps - Die pictures
Post by: Noopy on June 05, 2022, 06:55:46 am
...

Very interesting!  :-+
I assume it´s ok for you if I add some of your thoughts to my website.  :-+
Title: Re: Opamps - Die pictures
Post by: magic on June 06, 2022, 04:23:45 pm
I assume it´s ok for you if I add some of your thoughts to my website.  :-+
It's all stuff you can find in Harris databook.

As far as I can see, this die is exactly HA-2520 or something pretty much equivalent. The circuit is easy to follow given the schematic, particularly when you notice that PNP collector connections are made in the form of P+ frame surrounding all the active area, so polarity of each transistor is readily visible.
Title: Re: Opamps - Die pictures
Post by: mawyatt on June 06, 2022, 05:01:20 pm
I wondered if it might be a dielectric isolated process.
Everything points to that. Isolation islands look very much like those on OPA627. And it has to be complementary because there are transistors that need to be PNPs for the circuit to work which don't look like the usual lateral PNPs and apparently work just fine at 20MHz.

One such process that's known to have existed in the '70s was owned by Harris and bingo, this chip appears to be rebadged HA-2520.
Harris 1977 linear databook contains an illustration of the dielectric isolation process and their vertical PNP structure.

Yes Harris was a champion of dielectric isolated substrates for bipolar chips using bonded wafers back then, later became known as UHF1 and UHF2. We tried using UHF2 in its early stages, but the process wasn't ready for actual chip design. Later Bell Labs offered access to a new junction isolated process which became known as CBIC-V2 and supported ~9.8GHz NPN and ~4.6GHz Vertical PNPs with thick gold top layer metallization. This was the process that Comlinear utilized in their Current-Mode Feedback amplifiers, Burr-Brown used in their high speed analog chips, and likely National and others. Analog Devices lured the process guru away to help develop their high speed complementary bipolar process. Later Harris was able to get UHF2 production ready but we had already moved to IBMs new SiGe BiCMOS process, since we wanted to integrate entire MW Transceivers with massive digital on a single chip, first one called "Emerald".

Edit: In case folks are interested here's a book about SiGe BiCMOS and shows our "Emerald" chip, our small research company was Insyte corporation.

Best,
Title: Re: Opamps - Die pictures
Post by: Noopy on June 06, 2022, 07:14:22 pm
Very interesting! Thanks!  :-+


I have updated my website:

https://www.richis-lab.de/Opamp49.htm#HA-2520 (https://www.richis-lab.de/Opamp49.htm#HA-2520)

 :-/O
Title: Re: Opamps - Die pictures
Post by: MegaVolt on June 08, 2022, 01:27:50 pm
LH0042CH

https://zeptobars.com/en/read/National-LH0042CH-hybrid-opamp-FET-SEM

(https://s.zeptobars.com/LH0042CH-all-HD.jpg)
Title: Re: Opamps - Die pictures
Post by: SeanB on June 08, 2022, 02:07:45 pm
Thanks, always wanted to open one of those.
Title: Re: Opamps - Die pictures
Post by: magic on June 08, 2022, 05:06:14 pm
I could swear I have seen this chip somewhere...
https://www.eevblog.com/forum/projects/opamps-die-pictures/msg3328500/#msg3328500 (https://www.eevblog.com/forum/projects/opamps-die-pictures/msg3328500/#msg3328500)

Nice SEM micrographs, though :-+
That would be tough to do in visible light.
Title: Re: Opamps - Die pictures
Post by: magic on June 08, 2022, 09:34:05 pm
The "83" JFET could be this, which was also available as a discrete monolithic pair. More information in National's discrete transistors databook.

The modified 741 probably wasn't sold separately :)
Title: Re: Opamps - Die pictures
Post by: Noopy on June 09, 2022, 07:41:21 am
Thanks, I have added that information to my website.  :-+

Yeah, a SEM would be nice...  ::)
Title: Re: Opamps - Die pictures
Post by: TiN on June 14, 2022, 11:30:54 pm
Want some more toasted opamps for photoshoot? I'm slowly adding to "Pile for Noopy magic"  :=\ .
Title: Re: Opamps - Die pictures
Post by: Noopy on June 15, 2022, 05:04:49 am
Want some more toasted opamps for photoshoot? I'm slowly adding to "Pile for Noopy magic"  :=\ .

Of course!  ;D
It will take some time till you see the pictures but I´m sure you have some interesing parts!  :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on July 02, 2022, 03:24:45 am
(https://www.richis-lab.de/images/Opamp/53x01.jpg)

One more 741, here we have an AD741 built by Analog Devices.


(https://www.richis-lab.de/images/Opamp/53x03.jpg)

Vee is directly connected to the case.


(https://www.richis-lab.de/images/Opamp/53x02.jpg)

Datasheet shows the metal layer of the die. Nice!  :-+


(https://www.richis-lab.de/images/Opamp/53x05.jpg)

(https://www.richis-lab.de/images/Opamp/53x04.jpg)

The die shows no differences to the picture in the datasheet. B741 seems to be an internal naming of the AD741. In the lower left corner there are some auxiliary structures and a single pinch resistor that can be contacted and measured.

The architecture of the circuit is designed to minimize thermal effects. The input stage is placed symmetrically around a central horizontal axis in the left area. In the center of the die is the voltage amplifier stage with the large compensation capacitor. At the right edge the output stage of the operational amplifier can be seen. If the power dissipation increases in this area, the distance and arrangement of the input amplifier will increase the temperature in its symmetrical branches relatively evenly. The story of the LT1013 (https://www.richis-lab.de/Opamp26.htm (https://www.richis-lab.de/Opamp26.htm)) schows this relation in more detail.


(https://www.richis-lab.de/images/Opamp/47x16.jpg)

The circuit is the same as we have seen in the CA741.

The resistor R4 contains a free contact which makes it possible to vary the operating point of the input amplifier by changing the metal position.


https://www.richis-lab.de/Opamp50.htm (https://www.richis-lab.de/Opamp50.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Daniel Perez LW1ECP on July 04, 2022, 10:52:04 pm
No doubt the bigger feature in an opamp is the frequency-compensation capacitor! Even 30pF in the 741 takes up so much real estate.
Title: Re: Opamps - Die pictures
Post by: David Hess on July 05, 2022, 02:53:17 am
No doubt the bigger feature in an opamp is the frequency-compensation capacitor! Even 30pF in the 741 takes up so much real estate.

It sure does take up space.  One of the improvements after the 741 was to add transconductance reduction to the input stage so that the compensation capacitor need only be 5 picofarads.  The smaller die also made dual and quad parts easier.

I think that is what was going on with the LM348 "quad 741".  Some schematics show what appears to be transconductance reduction at the cascode PNPs, and a much smaller compensation capacitance.  The same dynamic performance would result if the input stage current was then reduced which appears to be the case because the input bias current is claimed to be lower.

It can be difficult to go by the schematics and sometimes the specifications because I think often they just copied the 741 datasheet.  I have found several examples of this in the past.
Title: Re: Opamps - Die pictures
Post by: magic on July 05, 2022, 08:45:55 am
I think that is what was going on with the LM348 "quad 741".  Some schematics show what appears to be transconductance reduction at the cascode PNPs, and a much smaller compensation capacitance.  The same dynamic performance would result if the input stage current was then reduced which appears to be the case because the input bias current is claimed to be lower.
Yes, it appears to be using transconductance reduction and the plot below is how you know it.

Halving of input stage current would only increase broadband voltage noise by 3dB to ~30nV/rtHz. I suppose the diode-connected collectors of those split PNPs take (and waste) 75% of NPN current, accounting for the remining 6dB.
Title: Re: Opamps - Die pictures
Post by: David Hess on July 05, 2022, 09:33:02 am
I think that is what was going on with the LM348 "quad 741".  Some schematics show what appears to be transconductance reduction at the cascode PNPs, and a much smaller compensation capacitance.  The same dynamic performance would result if the input stage current was then reduced which appears to be the case because the input bias current is claimed to be lower.

Yes, it appears to be using transconductance reduction and the plot below is how you know it.

Halving of input stage current would only increase broadband voltage noise by 3dB to ~30nV/rtHz. I suppose the diode-connected collectors of those split PNPs take (and waste) 75% of NPN current, accounting for the remining 6dB.

I forgot about the input noise, so there you go.

I thought there was a later 741 which used transconductance reduction, smaller capacitor, and the same stage current so the slew rate would be boosted, but I could not find it.  Many of the later "741" replacements did do this, but have PNP input stages so they are not really 741s.  They are not single supply parts, but the input PNPs give them a wide differential input voltage range like a 741.  Examples include the quad RC4136 and dual RC4558.  The LM833 is another PNP input part like this but not intended as a 741 replacement.

What I do not understand about the PNP input parts is how they achieve low input bias current with the low hfe of the PNP transistors on an NPN process.  And if they use a process with real PNPs, then how do they achieve a wide differential input voltage range with a low base-emitter breakdown voltage?
Title: Re: Opamps - Die pictures
Post by: iMo on July 05, 2022, 09:50:30 am
Off topic: I wonder how the guys in 60ties and 70ties actually did the design of all those great opamps. Except they probably had some simulators handy (ie Spice2 came 1975) that would certainly require a special mindset, imho.. I messed with Spice in second half of 80ties in a cmos digital design, but I can hardly imagine myself to start with designing for example an OP07 today, but as BobW said - "every idiot can count to one"..  :D
Title: Re: Opamps - Die pictures
Post by: T3sl4co1l on July 05, 2022, 10:12:28 am
Breadboards. Discrete transistors do this stuff just fine... albeit at a fraction of the bandwidth/Icc figure-of-merit, and just don't breathe anywhere near the poor thing. ;D  Knowing how these things scale lets you get the compensation close, and some tuning of proto chips will finish the job.
Title: Re: Opamps - Die pictures
Post by: magic on July 05, 2022, 02:32:30 pm
I thought there was a later 741 which used transconductance reduction, smaller capacitor, and the same stage current so the slew rate would be boosted, but I could not find it.
No such thing existed because discarding a fraction of input stage current to ground reduces input stage transconductance and peak output current equally. LM358 has similar dynamic characteristics to µA741 despite being the poster child of so-called transconductance reduction; only noise is higher ;)

Many of the later "741" replacements did do this, but have PNP input stages so they are not really 741s.  They are not single supply parts, but the input PNPs give them a wide differential input voltage range like a 741.  Examples include the quad RC4136 and dual RC4558.  The LM833 is another PNP input part like this but not intended as a 741 replacement.

What I do not understand about the PNP input parts is how they achieve low input bias current with the low hfe of the PNP transistors on an NPN process.  And if they use a process with real PNPs, then how do they achieve a wide differential input voltage range with a low base-emitter breakdown voltage?
These are certainly not real 741s, and unlike 741 they have phase reversal.

Regarding PNPs, according to this (http://www.designinganalogchips.com/) "β in excess of 100" is achievable with good design. I also recall reading about a small trick which improves lateral PNP injection efficiency: extra doping of the emitter. I don't know if it is in widespread use.
Title: Re: Opamps - Die pictures
Post by: David Hess on July 05, 2022, 10:38:55 pm
Off topic: I wonder how the guys in 60ties and 70ties actually did the design of all those great opamps. Except they probably had some simulators handy (ie Spice2 came 1975) that would certainly require a special mindset, imho.. I messed with Spice in second half of 80ties in a cmos digital design, but I can hardly imagine myself to start with designing for example an OP07 today, but as BobW said - "every idiot can count to one"..  :D

They had kits with process transistors and used extra resistors and capacitors to simulate parasitic elements like trace resistance and junction isolation capacitance.  Bob Pease mentioned it in one of his articles and showed a photograph of an impressive rat's nest of parts and wiring.

I thought there was a later 741 which used transconductance reduction, smaller capacitor, and the same stage current so the slew rate would be boosted, but I could not find it.

No such thing existed because discarding a fraction of input stage current to ground reduces input stage transconductance and peak output current equally. LM358 has similar dynamic characteristics to µA741 despite being the poster child of so-called transconductance reduction; only noise is higher ;)

Not all of the stage current is grounded, and AC and DC balance is independent.  The stage current itself cannot be reduced because the input stage pole will then cause excessive phase shift, which demonstrates exactly why the input stage current of the 741 was set where it was.  Incidentally, the 741 design cheats since the series connection of the NPN/PNP input stage halves transconductance, increasing its pathetic slew rate beyond what it normally would have been.

I was wrong about an example not existing, since the National AN-A application note at the end shows exactly what the incomplete datasheet schematics of the LM348 quad 741 must have been doing, as shown below.  The datasheet LM348 schematics I have seen must be incomplete, but they do show something going on.

Quote
Many of the later "741" replacements did do this, but have PNP input stages so they are not really 741s.  They are not single supply parts, but the input PNPs give them a wide differential input voltage range like a 741.  Examples include the quad RC4136 and dual RC4558.  The LM833 is another PNP input part like this but not intended as a 741 replacement.

These are certainly not real 741s, and unlike 741 they have phase reversal.

They are not, but they were advertised as having "741 performance" which led to confusion.  One way to identify them is that their input bias current is reversed.
Title: Re: Opamps - Die pictures
Post by: magic on July 06, 2022, 09:12:22 am
I see no reason to assume that LM348 uses any mechanism other than shown in its datasheet. The technique of simply discarding 75% of input collector currents to ground definitely worked for LM358, and discarding them into the LM101A-type bias generator as shown on the first page would achieve the same effect for LM348.

The mechanism shown in AN-A fig. 29 does not change the GBW/SR ratio because it reduces both the AC and DC current available to drive the second stage by the same ratio of four.

LM348 has the same GBW/SR ratio as plain old µA741 so nothing revolutionary here either.

Incidentally, the 741 design cheats since the series connection of the NPN/PNP input stage halves transconductance, increasing its pathetic slew rate beyond what it normally would have been.
I guess you're right, it makes sense.
Moreover, GBW/SR is typically near 3 for simple bipolar opamps with input stage current mirror and Miller compensation, but 741 datasheet gives a ratio of 2.
Title: Re: Opamps - Die pictures
Post by: tggzzz on July 06, 2022, 09:35:43 am
I suspect this is an opamp. Similar pretty pictures at https://entertaininghacks.wordpress.com/2015/07/07/images-of-late-70s-burr-brown-thick-film-hybrid-ics/

(https://entertaininghacks.files.wordpress.com/2015/07/burrbrown02.jpg)
Title: Re: Opamps - Die pictures
Post by: David Hess on July 06, 2022, 01:52:21 pm
I see no reason to assume that LM348 uses any mechanism other than shown in its datasheet. The technique of simply discarding 75% of input collector currents to ground definitely worked for LM358, and discarding them into the LM101A-type bias generator as shown on the first page would achieve the same effect for LM348.

The reason is that a quad 741 would not be economical because of the large area, and some LM348 schematics show a smaller compensation capacitance and incomplete transconductance reduction elements.  The same applies to the 324; most of the schematics do not show it but some do, including old contemporary alternatives to the 324.

The AN-A explains why the 348 uses a different method than the 324, although not why the 324 does not.  (1) If the current was simply discarded to reduce transconductance, then the current mirror operating at a lower current would limit performance.  The design in the 348 preserves mirror performance by removing the AC signal from the current mirror; not all of the excess collector current is returned to negative.

(1) Which makes me wonder if existing 324 schematics left out what was really going on.  I have found a few examples of schematics which were either simplified or misleading with the apparent intention to keep secrets.

Quote
The mechanism shown in AN-A fig. 29 does not change the GBW/SR ratio because it reduces both the AC and DC current available to drive the second stage by the same ratio of four.

Operating the current mirror at a higher current or bypassing AC around the mirror will change the performance for a given collector current, but does that alter the GBW/SR ratio?  Is there some other mechanism to do that?

I need to dig out my Burr-Brown books on operational amplifier design, but I do not think they cover this type of transconductance reduction.

Quote
LM348 has the same GBW/SR ratio as plain old µA741 so nothing revolutionary here either.

I think they did that deliberately to maintain compatibility.  It and similar chips were suppose to be exact replacements as much as possible.

Did all of the "faster" alleged 741 parts use PNP inputs?  Why were they faster?  I do not think we have complete schematics of any of them.

Title: Re: Opamps - Die pictures
Post by: magic on July 06, 2022, 05:16:42 pm
I suspect this is an opamp.
The bottom looks like Darlington emitter follower output stage, whatever the rest might be.

The AN-A explains why the 348 uses a different method than the 324, although not why the 324 does not.  (1) If the current was simply discarded to reduce transconductance, then the current mirror operating at a lower current would limit performance.  The design in the 348 preserves mirror performance by removing the AC signal from the current mirror; not all of the excess collector current is returned to negative.

(1) Which makes me wonder if existing 324 schematics left out what was really going on.  I have found a few examples of schematics which were either simplified or misleading with the apparent intention to keep secrets.
The situation regarding 324/358 is clear because there are die images: National (https://www.richis-lab.de/HDD_WD_Caviar_22500.htm#LM358), TI (https://zeptobars.com/en/read/TI-LM358-dual-general-purpose-opamp), Chinese clone (https://www.eevblog.com/forum/beginners/opamp-input-offsets-working-in-the-opposite-direction-to-what-i-expect/msg2680314/#msg2680314), more clones (https://www.eevblog.com/forum/projects/whats-inside-the-cheapest-and-fakest-jellybean-opamps/).
They unceremoniously dump 75% of each transistor's current right to the substrate. The only accurate schematic has been published by Samsung, see here (https://www.eevblog.com/forum/projects/whats-inside-the-cheapest-and-fakest-jellybean-opamps/msg2956990/#msg2956990).

There is a slightly different variant shown in Motorola/ON datasheets and implemented by ST (https://zeptobars.com/en/read/ST-TS321-SOT23-opamp-LM358A-LM324) - here the 75% collector is connected to the base and biases the preceding emitter follower.

In both cases, the NPN mirror runs at reduced current and this appears to be good enough. Hence, LM348 may be working like that too. Or it may not, there is only one way to know for sure.

Did all of the "faster" alleged 741 parts use PNP inputs?  Why were they faster?  I do not think we have complete schematics of any of them.
Well, Harris HA-2520 had NPN inputs...

More seriously, the published schematic of Raytheon's "improved 741" types is accurate. Again, see RC4558 on Zeptobars, or a Toshiba clone annotated by Noopy here (https://www.richis-lab.de/Opamp28.htm). They reduced compensation capacitor size simply by being faster. How were they faster, I don't know, apparently lateral PNPs got somewhat better in the '80s.
Title: Re: Opamps - Die pictures
Post by: David Hess on July 07, 2022, 01:20:54 am
They unceremoniously dump 75% of each transistor's current right to the substrate. The only accurate schematic has been published by Samsung, see here (https://www.eevblog.com/forum/projects/whats-inside-the-cheapest-and-fakest-jellybean-opamps/msg2956990/#msg2956990).

Go back further and Fairchild published a full schematic.  They had a competitor to the 324 which added class-AB biasing of the output stage.  I do not know why that series of parts did not become popular.  George Erdi worked at Fairchild, so I suspect a connection with the later LT1006/LT1013/LT1014.

Quote
There is a slightly different variant shown in Motorola/ON datasheets and implemented by ST (https://zeptobars.com/en/read/ST-TS321-SOT23-opamp-LM358A-LM324) - here the 75% collector is connected to the base and biases the preceding emitter follower.

I saw that but thought the base connection might be used for anti-saturation.

Quote
Did all of the "faster" alleged 741 parts use PNP inputs?  Why were they faster?  I do not think we have complete schematics of any of them.

Well, Harris HA-2520 had NPN inputs...

Harris had a process with dielectric isolation for their space products which they could apply to higher performance commercial products.  Dielectrically isolated processes do not suffer from radiation induced photocurrents generated in the substrate like junction isolated processes do.

Quote
More seriously, the published schematic of Raytheon's "improved 741" types is accurate. Again, see RC4558 on Zeptobars, or a Toshiba clone annotated by Noopy here (https://www.richis-lab.de/Opamp28.htm). They reduced compensation capacitor size simply by being faster. How were they faster, I don't know, apparently lateral PNPs got somewhat better in the '80s.

I thought that might have something to do with a better processes moving the current mirror poles to higher frequency, but those parts were also built by other manufacturers and there is no getting around the PNPs having to be improved.  Thanks for pointing out that the schematics show the correct configuration of the input stage.
Title: Re: Opamps - Die pictures
Post by: Noopy on July 10, 2022, 11:11:47 am
(https://www.richis-lab.de/images/Opamp/54x01.jpg)

(https://www.richis-lab.de/images/Opamp/54x02.jpg)

(https://www.richis-lab.de/images/Opamp/54x03.jpg)

One more comparator: The LM211 from National Semiconductor is functionally equivalent to the Fairchild µA311 (https://www.richis-lab.de/Opamp43.htm (https://www.richis-lab.de/Opamp43.htm)). Like the AMD AM211 (https://www.richis-lab.de/Opamp46.htm (https://www.richis-lab.de/Opamp46.htm)) it offers a slightly extended operating temperature range compared to the LM311 (-25°C to +85°C vs. 0°C to 75°C). The LM111 is even better specified allowing operation between -55°C and +125°C.


(https://www.richis-lab.de/images/Opamp/54x04.jpg)

(https://www.richis-lab.de/images/Opamp/54x05.jpg)

The schematic shown in the datasheet matches that of Fairchild's µA311. The design of the die appears very similar too. However, some elements are designed and arranged a little different. An additional bondpad for the output potential was created at the lower edge of the die.


(https://www.richis-lab.de/images/Opamp/54x07.jpg)

In the lower right corner you can see the revisions of six masks and some elements that allow to monitor the manufacturing process.


(https://www.richis-lab.de/images/Opamp/54x06.jpg)

The numbers 111 in the upper left corner refer to the best bin LM111. If these specifications are achieved you can tell after final testing.

I don´t know what the letter H should tell us. Perhaps it is a superior revision of the design.  :-//


https://www.richis-lab.de/Opamp51.htm (https://www.richis-lab.de/Opamp51.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on July 14, 2022, 12:34:27 pm
(https://www.richis-lab.de/images/Opamp/55x01.jpg)

(https://www.richis-lab.de/images/Opamp/55x02.jpg)

The LM310 is a voltage follower from National Semiconductor. We had already the LM310 built by Silicon General (https://www.richis-lab.de/Opamp08.htm (https://www.richis-lab.de/Opamp08.htm)) and the LM310 built by AMD (https://www.richis-lab.de/Opamp12.htm (https://www.richis-lab.de/Opamp12.htm)).


(https://www.richis-lab.de/images/Opamp/55x03.jpg)

(https://www.richis-lab.de/images/Opamp/55x04.jpg)

The edge length of the die is 1,2mm. Revisions of five masks are shown on the right edge. The numbers 110 refer to the LM110, the best bin of the voltage follower. The letters KB could be initials of a developer.

The design is similar to the AMD LM310 just the individual elements sometimes have a slightly different structure. In the Silicon General LM310 the bondpads and the circuit blocks are very similar, partly arranged in the same way, but bigger differences can be found.


(https://www.richis-lab.de/images/Opamp/55x05.jpg)

In the lower left area of the die is an element that could be a test structure. The buildup and function remain unclear.  :-//


https://www.richis-lab.de/Opamp52.htm (https://www.richis-lab.de/Opamp52.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on July 27, 2022, 03:27:01 am
(https://www.richis-lab.de/images/Opamp/56x01.jpg)

ST Microelectronics sells a µA741 variant under the designation UA741.


(https://www.richis-lab.de/images/Opamp/56x02.jpg)

The data sheet contains a circuit diagram. You can immediately see that some lines are missing there.  ???

It is basically the same schematic as for the SGS ATES L141 (https://www.richis-lab.de/Opamp42.htm (https://www.richis-lab.de/Opamp42.htm)). This is hardly surprising, since ST Microelectronics emerged from SGS ATES, among others.


(https://www.richis-lab.de/images/Opamp/56x03.jpg)

(https://www.richis-lab.de/images/Opamp/56x04.jpg)

The design of the device is similar to the SGS ATES L141 (https://www.richis-lab.de/Opamp42.htm (https://www.richis-lab.de/Opamp42.htm)) and the Sescosem SFC2741 (https://www.richis-lab.de/Opamp07.htm (https://www.richis-lab.de/Opamp07.htm)). Both companies have been merged into ST Microelectronics. Apparently ST didn´t want to take over the µA741 variant of one of the two completely. Perhaps the design came from Thomson Semiconducteurs. This company was also integrated into ST Microelectronics.


(https://www.richis-lab.de/images/Opamp/56x05.jpg)

The die shows the ST Microelectronics logo. In 1988 however the name of the company was still SGS Thomson. Probably the design was revised later and the ST logo was added in this context.


(https://www.richis-lab.de/images/Opamp/56x08.jpg)

(https://www.richis-lab.de/images/Opamp/56x06.jpg)

The character strings 2741.C and P728 are found on the edges. The latter is integrated into the metal layer in several deeper layers at a different location. This suggests that P728 is the internal designation for the design.


(https://www.richis-lab.de/images/Opamp/56x07.jpg)

The revisions of eight masks are documented on the side. According to this the design was revised twice.


https://www.richis-lab.de/Opamp53.htm (https://www.richis-lab.de/Opamp53.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on August 07, 2022, 03:22:26 am
(https://www.richis-lab.de/images/Opamp/57x01.jpg)

(https://www.richis-lab.de/images/Opamp/57x02.jpg)

(https://www.richis-lab.de/images/Opamp/57x03.jpg)

I had a National Semiconductor LM709 built 1967 (https://www.richis-lab.de/Opamp20.htm (https://www.richis-lab.de/Opamp20.htm)). Now this one was built 1969.


(https://www.richis-lab.de/images/Opamp/57x04.jpg)

(https://www.richis-lab.de/images/Opamp/57x06.jpg)

(https://www.richis-lab.de/images/Opamp/57x05.jpg)

The construction of the dies is very similar to the LM709 from 1967. The same elements can be found in the same circuitry. However, it is also clear that the arrangement was slightly revised and most likely a different manufacturing process was used.


https://www.richis-lab.de/Opamp54.htm (https://www.richis-lab.de/Opamp54.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: RoGeorge on August 07, 2022, 08:00:10 am
Great pics as always, thanks again!  :-+

More from the year 1969:  8)
https://www.historic-newspapers.com/blog/a-year-in-history-timeline-of-1969-events/ (https://www.historic-newspapers.com/blog/a-year-in-history-timeline-of-1969-events/)
Title: Re: Opamps - Die pictures
Post by: Noopy on August 13, 2022, 09:20:20 pm
(https://www.richis-lab.de/images/Opamp/58x01.jpg)

The HS-1135RH is a radiation hard operational amplifier originally developed by Harris Semiconductor and now produced by Intersil. The input resistance is 2MΩ. With a current consumption of 6,9mA the HS-1135RH offers a 3dB bandwidth of 350MHz and a maximum slewrate of 1,2kV/µs.


(https://www.richis-lab.de/images/Opamp/58x02.jpg)

The HS-1135RH offers an adjustable limit for the output level. The datasheet shows the part of the circuit which does the high level clamping. Vh determines via the transistors Qn6, Qp6, Qp5 and Qn5 at which voltage current is diverted from the input of the output buffer. The opamp flips back to normal operation in less than a nanosecond.


(https://www.richis-lab.de/images/Opamp/58x03.jpg)

(https://www.richis-lab.de/images/Opamp/58x04.jpg)

The datasheet describes the die of the HS-1135RH in more detail. The upper metal layer is shown there too. Accordingly 89 transistors were integrated on an area of 1,50mm x 1,48mm. The process used for this is called UHF-1. A bonded wafer with dielectric isolation is used. The special structure prevents latchup due to free charges, which can be generated by radiation.


(https://www.richis-lab.de/images/Opamp/58x14.jpg)

A description of the UHF-1 process can be found in the paper "UHF-1: A High Speed Complementary Bipolar Analog Process on SOI" published in the 1992 IEEE Bipolar Circuits and Technology Meeting. The process features two polysilicon layers and two metal layers. The high performance PNP transistors are particularly highlighted. The cutoff frequency of a NPN transistor is typically 9GHz, while the cutoff frequency of a PNP transistor is 5.5GHz. The gain factor is specified as 100 (NPN) and 40 (PNP).

The publication shows the structure of a PNP transistor, which has been recolored for better understanding. The basis is formed by two wafers which are connected by an insulating oxide layer. The upper wafer is first heavily p-doped, where it later functions as the collector lead (dark red).

The heavily doped and correspondingly low-resistance collector feed line is an important foundation for building PNP transistors with good specifications. In older DI processes it was not possible to integrate a deep heavily p-doping layer. According to the IEEE publication this was because such a p-dopant would have had to be introduced earlier in the process. The following process steps with their high temperatures would then lead to an unfavorable distribution of the doping.

In the UHF-1 process after building the collector feed line the epitaxial deposition of a weaker p-doped layer takes place which later represents the collector region (red). After this step the isolation of the active regions is completed. For this purpose a process creates deep trenches leading up to the isolation layer between the wafers. The trenches are lined with silicon oxide and filled with polysilicon.

The epitaxially applied collector layer is etched down a little around the active region of the transistor and is filled with a thick oxide layer. This reduces the base-collector capacitance and the base-substrate capacitance. The first polysilicon layer (yellow) contains an n-dopant which is allowed to diffuse into the underlying silicon as a base feed (dark blue). The actual base doping is then introduced into the active region (light blue). Due to its structure the transistor structure is self-aligned.

The second polysilicon layer (dark yellow) which is applied onto the base layer brings in the emitter doping (dark red). Apart from the inverted dopants, an NPN transistor has the same structure.

In addition to two metal layers (light green/dark green) the UHF-1 process also offers NiCr resistors that can be adjusted.


(https://www.richis-lab.de/images/Opamp/58x05.jpg)

(https://www.richis-lab.de/images/Opamp/58x06.jpg)

In the housing there is a small rectangular block next to the die which makes it easier to contact the bottom of the housing and thus the substrate. This contact is particularly important here as the substrate would otherwise be isolated and have an undefined potential.


(https://www.richis-lab.de/images/Opamp/58x15.jpg)

At the very top of the die you can see a layer that is about 10µm high. This is probably the upper isolated layer of the wafer. In the case of OPA627 (https://www.richis-lab.de/Opamp22.htm (https://www.richis-lab.de/Opamp22.htm)) the insulated layer appeared to be 20µm high.


(https://www.richis-lab.de/images/Opamp/58x07.jpg)

(https://www.richis-lab.de/images/Opamp/58x08.jpg)

The circuit is still relatively clear.


(https://www.richis-lab.de/images/Opamp/58x09.jpg)

In the upper right corner is the Harris Semiconductor logo. The number 93 probably stands for the year 1993, one year after the IEEE publication. 50749A03 could be the internal designation of the design. 21C, 22B, and 23B appear to be the mask designations and revisions for the two metal layers and the vias in between. SRJ and RJD could be abbreviations of the developers.


(https://www.richis-lab.de/images/Opamp/58x10.jpg)

The various patterns on the upper edge of the die show that a large number of masks were used. The patterns make it possible to check the alignment of the masks.


(https://www.richis-lab.de/images/Opamp/58x11.jpg)

The two test structures in the lower right corner of the dies certainly represent an NPN and a PNP transistor. Visually the structures can just be guessed. The many layers create an irregular surface structure that makes it difficult to recognize the relevant contours.


(https://www.richis-lab.de/images/Opamp/58x13.jpg)

(https://www.richis-lab.de/images/Opamp/58x12.jpg)

A large testpad is specially marked "NO BOND". From there a line leads around the circumference of the die to the negative supply potential. In the upper right corner, there are two orthogonally arranged resistors in this line. One can only speculate about the purpose of this long line. Perhaps the path is used when resistors are balanced.

In the lower left corner two resistors are integrated, which can be measured via testpads.


(https://www.richis-lab.de/images/Opamp/58x16.jpg)

Even though the circuit is difficult to analyze in detail due to the two polysilicon and the two metal layers, it is quite easy to guess that the actual opamp is located in the middle of the die. It seems to be the classic setup with the circuit symmetrically arranged around the center. On the right the larger output stage transistors can be seen. A bit further to the left, two capacitors are integrated, which most likely realize the frequency compensation.


(https://www.richis-lab.de/images/Opamp/58x17.jpg)

A large part of the area is taken up by a resistor array, which is most likely used for an offset adjustment. Traces of an adjustment process can be seen.

Surprisingly large protection structures are integrated at the signal inputs and at the clamping inputs.


https://www.richis-lab.de/Opamp55.htm (https://www.richis-lab.de/Opamp55.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on August 30, 2022, 10:06:11 am
(https://www.richis-lab.de/images/Opamp/59x01.jpg)

The LT1012 is a precision operational amplifier which is advertised in the datasheet as a better alternative to the OP07 (https://www.richis-lab.de/DAC07.htm#OP-07 (https://www.richis-lab.de/DAC07.htm#OP-07)). Accordingly, the maximum offset voltage is 25µV with a maximum temperature drift of 0,6µV/°C. The bias current remains below 100pA. Between 0.1Hz and 10Hz, the noise voltage is a maximum of 0.5µVpp. A supply of +/-1.2V is sufficient for the LT1012. The current consumption is 500µA maximum. The cutoff frequency for this is just over 500kHz with a slew rate of 0.2V/µs maximum. With a feedforward compensation up to 10V/µs can be achieved.


(https://www.richis-lab.de/images/Opamp/59x11.jpg)

To understand how the LT1012 works it is worth taking a closer look at the patent US4575685. Behind it are the almost legendary names Robert C. Dobkin, George Erdi and Carl T. Nelson.

With the above picture the patent represents the state of the art to reduce the bias current of an operational amplifier. The collector lines of the input transistors Q1/Q2 contain the transistors Q3/Q4. If the transistors have the same structure, the base current of Q3/Q4 corresponds to the base current of Q1/Q2. Transistors Q7/Q8 mirror this current to the inputs where it compensates for the bias current.

In practice, however, leakage currents occur, indicated here by the current sinks IL7/IL8. As a result current flows away from the base of Q7 and Q8 which negatively affects the compensation current. The typical lateral PNP transistors have a large contact area between the base region and the substrate or the insulation surfaces. Relevant leakage currents occur there especially at high temperatures. Another disadvantage of the above circuit is that it is influenced by the common mode voltage at the inputs. Nevertheless it is quite sufficient for many operational amplifiers. However, if you want to work with very small input currents, you have to improve the bias compensation.


(https://www.richis-lab.de/images/Opamp/59x10.jpg)

Patent US4575685 deals with a circuit that compensates the bias currents more precisely, but is also considerably more complex. The transistors marked with an S are so-called "super-beta transistors". These transistors offer a very high gain factor in the range between 1.000 and 10.000. In addition, they can be manufactured with very similar electrical characteristics, which is particularly helpful here.

The additional current sink Q21 determines with the current mirror Q14 that the same current I flows in direction Q13/Q10 as to each of the input transistors Q11/Q12. The interconnection of Q13/Q10/Rp ensures that a base current is established at Q10 so that current I can flow out via Rp. Q13 does not form a current mirror in the classical sense. Q14 drives current through the emitter of Q13 until enough current flows through its collector C to drive Q10 to the point where current I flows through its collector. The base current of the super-beta transistor is so small that it can be neglected.

Q13 now transfers currents to the inputs via its collectors A and B which correspond to the base current of Q10. Since Q10 has the same structure as the input transistors Q11/Q12 and also conducts current I, the base currents of all three transistors are equal and the currents of Q13 can compensate for the bias currents at the inputs. The collector D is not needed and is just present so that the transistor can be constructed symmetrically. As a lateral PNP transistor Q13 suffers from the same leakage currents as the PNP transistor of the first circuit but here they are fed by Q17 and thus do not affect the compensation of the bias currents.

The patent specifically notes the importance of current mirror Q14. If the voltage at the inputs reduces faster than 0,1V/us the capacitance at the base of Q10 would be sufficient for Q10 to take most of the current from Q20. The operating point of Q11/Q12 would shift due to the lack of current and the transfer characteristics would deteriorate. The capacitance at the base is typically no more than 20fF. However, the base current discharging this capacitor is also just 0,5nA to 2nA due to the super beta transistor. Since Q14 limits the current through Q10 to the value I Q10 not only is prevented from taking current from the input transistors Q11/Q12. Q10 thereby saturates which increases the base current and quickly discharges the parasitic capacitance there. This ensures that when the voltage at the inputs changes rapidly the bias current does not fluctuate.

In order for transistors Q11/Q12/Q10 to behave as equally as possible their collector-base voltages should be equal. It is also advantageous if the voltage is small and independent of the common mode voltage at the input. The collector-base voltage of Q11 is determined by the base-emitter voltages of Q19/Q9/Q15/Q11. According to the patent the different current values and transistors provide a collector-base voltage in the range of 0.1-0.2V.
The collector-base voltage of Q10 is defined by the path Q15/Q16/Q18/Q17/Q13/Rp. The same voltages are present at Q10 and Q11 if the base-emitter voltage of Q13 has the same value as the sum of the base-emitter voltage of Q18 and the voltage drop across Rp. Although these are very different elements, the patent states that this requirement is satisfied relatively well even at different temperatures.

The surrounding current sources and sinks must, of course, be constructed so that the necessary currents are established. Below the differential amplifier these are not 2I but 3I due to the additional transistor Q10. According to the patent the same current does not necessarily have to flow in the right-hand branches Q21/Q22 as in the input transistors, but the currents must be constantly proportional to each other. The ratio, which also affects the base currents, can then be corrected via the resistors A' and B'.

The Z-diodes Z1 and Z2 represent fuses that can be triggered in production and make it possible to adjust the current ratio of Q20 to Q21/Q22 accordingly. Thus the strength of the bias current compensation can be adjusted.


(https://www.richis-lab.de/images/Opamp/59x02.jpg)

The datasheet contains a circuit diagram, which is much easier to understand with the above background information. As usual the biasing of the different circuit parts is done by a series of current mirrors (blue). The generation of the reference current is surprisingly complex.

The input transistors in the differential amplifier (light green) are super beta transistors. The very high current gain factor is of course extremely advantageous for the input transistors. At the collector resistors the trim pins are connected, which allow an adjustment of the offset from outside the package.

The cyan circuit, as described in the patent above, ensures that the collector-base voltage of the input transistors Q1/Q2 remains constant. The dark red circuit part maps the compensation of the bias current, also described in the above patent.

In addition to the bias current compensation, the differential amplifier features Q9/Q10 (purple) and Q39 (pink). Q9 and Q10 serve as clamping diodes, limiting the input voltage between -IN and +IN. The purpose of the connection to the cyan circuit remains unclear. Current can flow across this connection only if an input potential becomes lower than the emitter potential of the input transistors.
Q29 gives you three diodes, which apparently should accelerate the clearing of the free charge carriers in the super beta transistors. What is otherwise more relevant for power transistors could also be helpful here due to the high gain factors.

The voltage amplifier (yellow) is based on transistor Q22. Via pin 5 the frequency compensation can be extended externally. Q24/Q24 (orange) generate the voltage drop, which provides some quiescent current in the output stage. Q21 is driven inventoried to Q22 and can take over its current, which makes the highside of the output stage activate faster.

Q25 and Q28 represent the drivers of the power stage (gray). If the voltage amplifier stage supplies more current Q25 conducts more current and the level of Q28 decreases. This means that Q42, the lowside transistor of the output stage, is driven less. At the same time, more current flows from Q30 into the highside transistor of the power amplifier stage (Q43) and drives it harder.
If the voltage amplifier stage reduces the current, the excitation of Q25 decreases, more current flows out of Q42, and the output of the opamp swings toward the negative supply potential. At the same time Q28 conducts more current and reduces the excitation of the highside transistor.

The complementary output stage (red) is equipped with an overcurrent protection circuit (Q37/Q38). The 100Ω resistor at the output improves the behavior with capacitive loads.

Between driver and output stage there are further protection circuits (dark green). Q26 becomes conductive when the output has a high potential and the lowside transistor of the output stage is driven strongly. As a consequence, Q41 and Q40 become conductive, which reduces the output level. This ensures that transistor Q42 is not loaded beyond its SOA range.
Q27 reacts similarly. The output potential is applied to its emitter via Q28 and Q42. If this potential is very low and a high current flows across the 1,5kΩ resistor at the same time, Q27 sinks the base current of the highside transistor. Q29 simultaneously reduces the current flow through Q25, which means that the hihgside transistor is driven even less hard.


(https://www.richis-lab.de/images/Opamp/59x03.jpg)

One bondwire connects the pin of the negative supply to the housing.


(https://www.richis-lab.de/images/Opamp/59x04.jpg)

The Die ist 1,8mm x 1,6mm.


(https://www.richis-lab.de/images/Opamp/59x09.jpg)

The design dates from 1987. The B could indicate a second revision.  :-//


(https://www.richis-lab.de/images/Opamp/59x08.jpg)

The milling path contains the revisions of nine masks and some patterns that allow to check the alignment of the masks against each other.

The circuit includes several Zener fuses. A metal fuse is integrated between the negative supply potential and a testpad which does not interfere with the circuit. Presumably it was triggered during alignment, perhaps to indicate the quality level.


(https://www.richis-lab.de/images/Opamp/59x05.jpg)

Most of the elements are easy to identify on the die. The round testpads in the upper left corner allow to adjust the offset of the input stage. The rectangular testpads on the bottom edge give you the opportunity to adjust the bias current compensation.

The input stage is arranged to have a low temperature drift. The input transistors Q1/Q2 are doubled up and arranged crosswise in the center. On the far left they keep a large distance from the output stage on the right edge, where the most power dissipation occurs. Even the collector resistors are integrated in the center at the left edge. To the right the electrically following transistors up to the voltage amplifier are arranged around the middle of the die.

The circuit corresponds mostly to the schematic in the datasheet, but there are some minor differences (light green). The pinch resistor RQ15 is found at the collector of Q15, which is the resistor referred to as Rp in the patent specification.
The resistor RQ13 is located between Q13 and Q16, this seems to be just an undercrossing of a line. At this point, a resistor has little effect on the circuit.
The 50kΩ resistor connected at one end to the clamping diodes at the input does not lead to the upper but to the lower end of the 1,5kΩ resistor above Q12.

In the collector of Q22 there is the resistor RQ22. It seems that here one wanted to create a symmetry to the second transistor of the voltage amplifier stage. Behind this resistor the line is formed into a relatively large area, which represents some capacitance to the negative supply potential (CQ22).

At the base of Q29 there is the resistor strip RQ29, but this probably serves just as an undercrossing.

Also not shown in the schematic is the transistor Q20b, which is a base current compensator for transistor Q20, which operates as a current mirror.


(https://www.richis-lab.de/images/Opamp/59x07.jpg)

On closer inspection the large capacitor has a somewhat more complex structure than shown in the datasheet. The capacitance of 30pF is set between the metal layer and the green n-doped layer underneath. The edge surrounding the metal layer shows that there is a thinner oxide layer under the metal layer, which increases the capacitance. The metal surface has an area that can be separated via a thin contact. This makes it easier to adjust the capacitance if necessary.

The dark p-doped surface on which the capacitor is placed is connected to the emitter of Q25. Electrically adding capacitance to this node seems to have no effect on the circuit. For a safe isolation of the capacitor one could have simply connected the area to the negative supply. Probably this measure was taken to keep the parasitic capacitance to the substrate away from the voltage amplifier stage. Since it is a pn junction, this capacitance would fluctuate with the signal level and could thus cause distortion. The potential of the emitter of Q25, on the other hand, is constantly one base-emitter voltage below the potential of the collector of Q22.

The inner, green layer of the capacitor is most likely the emitter doping. It is embedded in the dark layer which is then represented by the base doping. Surrounding the whole structure is a green frame, most likely the collector doping, and finally the dark isolation frame. On the right side of the picture, the emitter potential of Q43 contacts the capacitor area. The lead is connected to a strip of the base material. Thus the collector area should be at about the same potential as the base area under the capacitor and the 30pF capacitor is thus maximally well shielded. The metal surface to the left of the Q43 contact seems to connect the collector surface to the buried collector.


(https://www.richis-lab.de/images/Opamp/59x13.jpg)

If one inserts the transistors in the correct size ratio into the circuit diagram of the patent an interesting picture emerges. The current sinks Q20/Q21/Q22 are constructed in the specified ratio of 3:1:1. The same current density ensures maximum synchronism.

The doubled super beta transistors Q11/Q12 at the inputs are relatively large. To ensure the same current density in transistor Q10 it has two emitter areas. The super beta transistor Q18 is smaller but still large for an NPN transistor. The other NPN transistors Q15/Q16/Q17/Q9 are rather inconspicuous.

The symmetrical structure of the PNP transistor Q13 can be seen well. One of the collectors is led back to the base. The PNP transistor Q14 has to carry more current and is designed accordingly larger. The upper metal surface directly connects the upper collector surface with the base surface. The PNP transistor Q19 has an unusual design. Two p-doped areas, one slightly longer, are located in an n-doped area which carries the base potential.


(https://www.richis-lab.de/images/Opamp/59x06.jpg)

The two 800Ω resistors above the large collector resistors are amazingly complex. The input offset can be adjusted externally by the corresponding pins. In addition the testpads can be used to configure the resistors during manufacture.

Although there are just three testpads a total of 13 Zener fuses can be triggered. We have seen these series connected Zener fuses that can be triggered selectively in the LT1013 too (https://www.richis-lab.de/Opamp26.htm (https://www.richis-lab.de/Opamp26.htm)). In the LT1012 this technique has been used even more excessively. This reduces the need for testpads which saves a lot of space.


(https://www.richis-lab.de/images/Opamp/59x12.jpg)

The JFET generating the reference current for the current sinks and sources can only be guessed at a very close look. A strip leads from the positive supply potential over a relatively long distance. The edges of the stripe show up through the metal layer (white). Initially the material appears dark (red). Here the collector doping seems to be completely covered by the base doping. This would result in an n-doped channel with a p-doped cladding. On the last part of the strip (cyan) is a green layer, presumably the collector doping, which appears to be contacted away from the contact to the buried collector feed line. The purpose of this division remains open.  :-//


https://www.richis-lab.de/Opamp56.htm (https://www.richis-lab.de/Opamp56.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on September 04, 2022, 06:01:46 pm
(https://www.richis-lab.de/images/Opamp/60x01.jpg)

The OP07 was developed by Precision Monolithics and offers a very low offset voltage. The OP07C represented the worst bin at the time with a maximum offset voltage of 250µV, a longterm drift of typically 0,4µV/month (2,0µV/month maximum) and a voltage noise of typically 0,38µVpp (0,1Hz-10Hz; 0,65µVpp maximum). The OP07A variant was the best bin and offers a maximum offset voltage of just 45µV, a typical longterm drift of 0,2µV/month (1,0µV/month maximum) and a voltage noise of 0,35µVpp (0,6µVpp maximum). The operating voltage can be selected between +/-3V and +/-18V. The cutoff frequency is typically 0,6MHz, and the slewrate is specified at 0,17V/µs.


(https://www.richis-lab.de/images/Opamp/60x13.jpg)

The OP07 was advertised by PMI as early as 1976 in Electronic Design 16. Analog Devices produces this operational amplifier still today.


(https://www.richis-lab.de/images/Opamp/60x06.jpg)

The new datasheet from Analog Devices shows the same circuit diagram as the old datasheets from PMI. The differential amplifier at the input (blue) is equipped with diodes that limit the input voltage (Q21-Q24). The collector resistors contain taps connected to the offset pins. R2A and R2B are tuned during fabrication.

OP07 includes a bias compensation (green). As described with the LT1012 transistors Q3/Q4 carry the same currents as input transistors Q1/Q2 and accordingly draw similar base currents. Q5/Q7 and Q6/Q8 copy these currents and feed them into the inputs where they compensate the bias.

Between the input amplifier (blue) and the voltage amplifier stage (red) emitter followers are integrated as a buffer (purple). The signals are still differentially routed in this area. The voltage amplifier stage works against a current mirror (Q13/Q14). The frequency compensation is relatively complex (cyan). C2 represents the actual frequency compensation. C1 attenuates high frequencies in the uncompensated path. C3 implements feedforward compensation that bypasses the PNP transistors at high frequencies. According to "Precision Monolithics Linear & Conversion I.C. Products" from 1977 a total of 210pF was integrated into the OP07.

A driver stage (yellow) controls the push-pull output stage (dark red) which is permanently short-circuit proof according to the datasheet. The schematic doesn´t show any shortcircuit protection, but on the die a corresponding circuit can be seen. The gray circuit provides a certain voltage drop between Q19 and Q20 and thus generates the necessary quiescent current.


(https://www.richis-lab.de/images/Opamp/60x07.jpg)

The manual "Precision Monolithics Linear & Conversion I.C. Products" mentioned above shows the residual bias current and its variation over temperature. For even lower bias currents, more complex circuits are required, such as those integrated in the LT1012 (https://www.richis-lab.de/Opamp56.htm (https://www.richis-lab.de/Opamp56.htm)).


(https://www.richis-lab.de/images/Opamp/60x03.jpg)

The housing is directly connected to the negative supply potential.


(https://www.richis-lab.de/images/Opamp/60x04.jpg)

(https://www.richis-lab.de/images/Opamp/60x05.jpg)

The dimensions of the dies are 2,55mm x 1,35mm.


(https://www.richis-lab.de/images/Opamp/60x11.jpg)

"Precision Monolithics Linear & Conversion I.C. Products" shows the arrangement and function of the individual bondpads. The NC bondpads are used to adjust the offset voltage.


(https://www.richis-lab.de/images/Opamp/60x02.jpg)

On the die you will find the characters OP.07.Z. PMI marked revisions by counting up from Z to A. This means that the present design is the first one. In the AD1139, on the other hand, the revision U can be found (https://www.richis-lab.de/DAC07.htm#OP-07 (https://www.richis-lab.de/DAC07.htm#OP-07)). The year 1986 is shown on this die, so it is about 10 years older.


(https://www.richis-lab.de/images/Opamp/60x10.jpg)

The differences between revision Z and revision U are minimal and seem to be functionally irrelevant for the most part. Just resistor R7 in the driver of the power amplifier seems to have been lengthened somewhat.


(https://www.richis-lab.de/images/Opamp/60x12.jpg)

"Precision Monolithics Linear & Conversion I.C. Products" shows how to tune the offset voltage in the input stage. Four testpads allow to trigger four Zener fuses which subsequently bridge the collector resistors R2C, R2D, R2E or R2F. The resistor ratio defines the offset voltage.


(https://www.richis-lab.de/images/Opamp/60x09.jpg)

Several small resistors are integrated around the four testpads on the die. The somewhat larger areas containing the Zener fuses can be seen too.


(https://www.richis-lab.de/images/Opamp/60x08.jpg)

The exact structure of a Zener fuse can also be found in the "Precision Monolithics Linear & Conversion I.C. Products". It is a Zener diode, more precisely the base-emitter path of a NPN transistor. When the Zener fuse is triggered the structure is destroyed and shorted. The shortcircuit is formed by the melting of the surrounding metal into the intervening base-emitter path.


https://www.richis-lab.de/Opamp57.htm (https://www.richis-lab.de/Opamp57.htm)

 :-+
Title: Re: Opamps - Die pictures
Post by: iMo on September 04, 2022, 06:31:31 pm
FYI - I own several PMI OP07AY in DIL14 ceramic package, there is a picture I published here (I will find it).
Based on an old PMI datasheet I downloaded that AY version was with the best params (I will find the DS).
PS: the 1976 PMI OP07 datasheet
Title: Re: Opamps - Die pictures
Post by: Noopy on September 04, 2022, 06:57:29 pm
FYI - I own several PMI OP07AY in DIL14 ceramic package, there is a picture I published here (I will find it).
Based on an old PMI datasheet I downloaded that AY version was with the best params (I will find the DS).
PS: the 1976 PMI OP07 datasheet

Well the AY is the A in the DIL-Package with a higher temperature rating. So the AY is a little better. But the A is the best bin in the TO-99 package.
So you are right and I´m right too.  ;) ;D
Title: Re: Opamps - Die pictures
Post by: magic on September 04, 2022, 07:02:25 pm
There is a second level of cascode over the input stage, not shown in the datasheet, which ensures that the first level cascode transistors have the same collector-emitter voltage as the input pair. I suppose it improves base current cancellation accuracy over common mode input range and increases input impedance. OP-07 bias cancellation is exactly the "prior art" circuit shown in that LT1012 patent. (Good find, BTW, I never understood why LT1012 is so weird).

There is C4 in OP-07, going between the right-hand ends of C2 and C3. It implements Miller compensation of that internal 2-stage opamp-inside-opamp.

Complete schematic can be found in old datasheets from TI. Very ugly like most TI schematics and has some small errors in the output stage, but still quite helpful.
Title: Re: Opamps - Die pictures
Post by: iMo on September 04, 2022, 07:04:25 pm
Btw I've been using one of them actively in my 2xLT1021-10 ref source as the buffer. I will desolder it soon as the ref source with the epoxy LT1021 is a crap (large hysteresis).
When it gets damaged I will send it to you for autopsy.. :D
Title: Re: Opamps - Die pictures
Post by: Noopy on September 04, 2022, 07:10:39 pm
There is a second level of cascode over the input stage, not shown in the datasheet, which ensures that the first level cascode transistors have the same collector-emitter voltage as the input pair. I suppose it improves base current cancellation accuracy over common mode input range and increases input impedance. OP-07 bias cancellation is exactly the "prior art" circuit shown in that LT1012 patent. (Good find, BTW, I never understood why LT1012 is so weird).

There is C4 in OP-07, going between the right-hand ends of C2 and C3. It implements Miller compensation of that internal 2-stage opamp-inside-opamp.

Complete schematic can be found in old datasheets from TI. Very ugly like most TI schematics and has some small errors in the output stage, but still quite helpful.

You are right.  :-+
I didn´t check all the components but it was clear that there is some more than shown in the datasheet.
Can you give me a link to the old TI datasheet? I can´t find it. The newer one is no help.
Title: Re: Opamps - Die pictures
Post by: magic on September 04, 2022, 07:19:36 pm
It's very helpful if you want to know more about TI's version of LM741 ;D

This one is good.
http://www.elenota.pl/datasheet-pdf/49486/Texas-Instruments/OP07C (http://www.elenota.pl/datasheet-pdf/49486/Texas-Instruments/OP07C)

Even die image is included and it's authentic.
https://www.eevblog.com/forum/projects/decapping-ics-for-investigation/msg1118381/#msg1118381 (https://www.eevblog.com/forum/projects/decapping-ics-for-investigation/msg1118381/#msg1118381)
For some reason, it looks like more area is devoted to capacitors :-//

Generally, to find old TI datasheets, look at the TI literature number on the first page, like SLOS099G.
Then change the letter at the end, say SLOS099B, and just search for it.
Title: Re: Opamps - Die pictures
Post by: Noopy on September 04, 2022, 07:29:23 pm
Thanks for the link and for the explanation how to find the old datasheets.  :-+

I agree with you, the TI schematic looks more realistic.  :-+
As usual they don´t tell you everything.  ;D
Title: Re: Opamps - Die pictures
Post by: iMo on September 04, 2022, 07:30:38 pm
The TI's params looks worse than the PMI's..
I've learned a new wording in that TI's OP07 datasheet - "These chips, properly assembled, display characteristics similar to the OP07"..  :)
Title: Re: Opamps - Die pictures
Post by: Noopy on September 04, 2022, 07:31:32 pm
The TI's params looks worse than the PMI's..
I've learned a new wording in that datasheet - "These chips, properly assembled, display characteristics similar to the OP07"..  :)

 ;D ;D ;D
Title: Re: Opamps - Die pictures
Post by: Noopy on September 23, 2022, 08:35:56 pm
(https://www.richis-lab.de/images/Opamp/61x01.jpg)

The OP177 is a successor of the OP07 developed by Analog Devices (https://www.richis-lab.de/Opamp57.htm (https://www.richis-lab.de/Opamp57.htm)).

The maximum offset voltage was reduced a little to 100µV. The best sorting has an offset of typically 10µV, maximum 25µV. The open loop gain is higher by a factor of 10. The slew rate is minimally larger, and the bandwidth is specified as 0.6MHz, as with the OP07. The maximum power consumption was halved.


(https://www.richis-lab.de/images/Opamp/61x02.jpg)

The datasheet of the OP177 contains the same circuit diagram as shown in the datasheet of the OP07.


(https://www.richis-lab.de/images/Opamp/61x03.jpg)

There is a protective layer on the die, which is most likely made of polyimide. The testpads for adjusting the offset voltage are clearly visible.


(https://www.richis-lab.de/images/Opamp/61x04.jpg)

(https://www.richis-lab.de/images/Opamp/61x05.jpg)

The polyimide layer can only be decomposed with increased temperatures, while the metal layer also suffers somewhat.

The dimensions of the die are 2,3mm x 1,4mm. It is thus only minimally smaller than the die of the OP07. According to the labeling, it is an Analog Devices design dating back to 1987.


(https://www.richis-lab.de/images/Opamp/61x06.jpg)

As with the OP07 the schematic in the datasheet does not really match the circuit and it is better to refer to the schematic in the datasheet of the OP07 from Texas Instruments.

Superficially the OP177 resembles PMI's OP07. Obviously the more modern manufacturing processes were enough to improve the specifications.


(https://www.richis-lab.de/images/Opamp/61x07.jpg)

The OP177 has as many test pads and fuses for adjusting the offset voltage as the OP07. On the left edge you can see the dummy resistors flanking the big collector resistors.


https://www.richis-lab.de/Opamp58.htm (https://www.richis-lab.de/Opamp58.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: David Hess on September 23, 2022, 09:02:23 pm
There is a second level of cascode over the input stage, not shown in the datasheet, which ensures that the first level cascode transistors have the same collector-emitter voltage as the input pair. I suppose it improves base current cancellation accuracy over common mode input range and increases input impedance. OP-07 bias cancellation is exactly the "prior art" circuit shown in that LT1012 patent. (Good find, BTW, I never understood why LT1012 is so weird).

The LT1012 bias cancellation circuit was a real improvement over the OP-07 though.  It has improved AC response which was more relevant to faster parts like the LT1007 compared to the OP-27.  It may also have improved the noise performance.
Title: Re: Opamps - Die pictures
Post by: RoGeorge on September 23, 2022, 09:48:44 pm
The OP177 is a successor of the OP07 developed by Analog Devices

Some schematics, and tails and stories about George Erdi (μA725), and how he paved the road for the OP07 and later OP177 starting from page 57 of 74 in https://www.analog.com/media/en/training-seminars/design-handbooks/Op-Amp-Applications/SectionH.pdf, (https://www.analog.com/media/en/training-seminars/design-handbooks/Op-Amp-Applications/SectionH.pdf,) or the same chapter inside the AD Handbook http://www.miedema.dyndns.org/co/2018/Op_Amp_Applications_Handbook-Walt-Jung_2005.pdf (http://www.miedema.dyndns.org/co/2018/Op_Amp_Applications_Handbook-Walt-Jung_2005.pdf) (at page 61 of 970)".

Quote
A second thread of development for precision op amps started at roughly the same time
as the LM108 design, in 1969. Working then for Fairchild Semiconductor, George Erdi
developed the μA725, the first IC op amp to be designed from the ground up with very
high precision in mind.

In a rather complete technical paper on the 725 circuit and precision op amp design in
general, Erdi laid down some rules which have become gospel in many terms

...

In 1975, Erdi reported on an offset trim technique that used 300mA over-current pulses,
to progressively short zener diodes in a string. With the zener string arranged strategically
in the input stage load resistances of an op amp, this so-called "zener-zapping" could be
used to trim the offset of an op amp on the wafer (see Reference 26). The first op amp to
utilize this new trim technique was Erdi's OP07, which was introduced by PMI in 1975
(see Reference 27).

...

PMI went forward with the OP07 op amp evolution, and introduced the OP77, a higher
open-loop gain version of the OP07 in 1988. The best grade OP77A featured a typical
gain of ~142dB, an offset of 25μV, and a drift of 0.3μV/°C(max). Later, an additional
device was added to the roster, the OP177. This part offered similar performance to the
OP77A, as the OP177F, specified over the industrial temperature range.

Prior to the 1990 acquisition of PMI by ADI, the ADI designers turned out some
excellent OP07 type amplifiers in their own right. Designed by Moshe Gerstenhaber, the
AD707 essentially matched the OP77 and OP177 spec-for-spec, operating over
commercial and industrial ranges (see Reference 28). It was introduced in 1988.
Title: Re: Opamps - Die pictures
Post by: Noopy on September 24, 2022, 03:37:41 am
Some schematics, and tails and stories about George Erdi (μA725), and how he paved the road for the OP07 and later OP177 starting from page 57 of 74 in https://www.analog.com/media/en/training-seminars/design-handbooks/Op-Amp-Applications/SectionH.pdf, (https://www.analog.com/media/en/training-seminars/design-handbooks/Op-Amp-Applications/SectionH.pdf,) or the same chapter inside the AD Handbook http://www.miedema.dyndns.org/co/2018/Op_Amp_Applications_Handbook-Walt-Jung_2005.pdf (http://www.miedema.dyndns.org/co/2018/Op_Amp_Applications_Handbook-Walt-Jung_2005.pdf) (at page 61 of 970)".

Thanks!  :-+
I have corrected my website.
I should have known it´s a PMI part, the naming 1415X is characteristic for PMI.
Title: Re: Opamps - Die pictures
Post by: Noopy on October 06, 2022, 04:29:34 am
(https://www.richis-lab.de/images/Opamp/62x01.jpg)

The OP295 built by Precision Monolithic is a dual opamp, which is also available as a quad opamp with the designation OP495. The device gets by with a single supply voltage in the range between 3V and 36V, drawing just 150µA. Also worth mentioning is the extended operating temperature range of -40°C to 125°C.

The offset voltage is typically 30µV with a maximum of 300µV with a temperature drift of 1µV/°C and 5µV/°C respectively. These values apply to a supply voltage of 5V. At 3V and +/-15V the values are somewhat higher. The disadvantage of the low current consumption is the associated low slewrate of typically 0,03V/µs. Accordingly, the cutoff frequency is just 75kHz too (85kHz at +/-15V). The rail-to-rail output can deliver up to 15mA and remains stable with capacitive loads up to 300pF.


(https://www.richis-lab.de/images/Opamp/62x07.jpg)

In the datasheet the OP295 is referred to as a CBCMOS opamp. An explanation for this designation can be found in the IEEE publication "A high performance VLSI structure-SOI/SDB complementary buried channel MOS (CBCMOS) IC" published at the "20th European Solid State Devices Research Conference" in September 1990.

Two wafers with a silicon oxide surface are bonded together so that the unoxidized sides face outward. The top surface is then ground until the desired thickness is achieved. The transistors are located in areas that are insulated from each other and from the substrate with silicon oxide layers. This provides many advantages, such as lower leakage currents, lower parasitic capacitances, and higher robustness to radiation.

It is noteworthy that the transistors do not have an inversely doped channel compared to the drain and source like normal MOSFETs, but only contain different concentrations of one doping. According to the IEEE publication, if the channel is thin enough, the highly doped polysilicon ensures that the transistors are off even when not driven. As the gate-source voltage increases, the conductive channel forms not on the surface but inside the silicon (buried channel), which has a positive effect on the transistor's properties.

Nevertheless, the datasheet of the OPA295 reveals that bipolar transistors are used in its input stages.


(https://www.richis-lab.de/images/Opamp/62x02.jpg)

(https://www.richis-lab.de/images/Opamp/62x03.jpg)

The dimensions of the die are 2,0mm x 1,6mm. The design dates back to 1991. The characters 5511Y most likely represent one of PMI's typical internal project designations. Y stands for the second revision of the device.


(https://www.richis-lab.de/images/Opamp/62x06.jpg)

The die shows a certain symmetry but is not entirely symmetrical. The input and output bondpads of the two operational amplifiers (blue/red) are arranged approximately the same, but the input amplifiers are both located in the upper area of the die, for example. In the lower right corner an additional circuit is integrated, which probably does biasing of the circuits (green).


(https://www.richis-lab.de/images/Opamp/62x04.jpg)

Spread over the die, the mask revisions of nine masks can be found. That matches the IEEE paper above, which specifies nine lithography steps for the CBCMOS process. Two rows of squares in the upper left corner allow one to evaluate the imaging performance of the process.

On the right is a symbol that probably contains the initials of the developers. Similarly scrambled initials can also be found in the OP283 (https://www.richis-lab.de/Opamp19.htm (https://www.richis-lab.de/Opamp19.htm)).


(https://www.richis-lab.de/images/Opamp/62x05.jpg)

A lot of the elements on the die can be easily identified. The two distributed capacitors on the right and left edges are particularly striking. The effective capacitance can be varied with strips of the metal layer (green). A little further inside the die another capacitor is integrated for each opamp.

The offset voltage of the OP295 was adjusted to a minimum by laser trimming (red). The balanced resistors of the input stages show traces of this adjustment in one path each. Typical for laser trimming is the testpad in the lower left corner of the die. It is equipped with a target mark and a strip of the resistor material and serves to adjust the laser.

What remains unclear is the function of the large green area connected with the negative supply potential and with the bias circuit. It could be a row of J-FETs with the green layer representing the gate electrode. However, in this case the upper JFET row would not have been necessary and the central area also seems unnecessarily large.


https://www.richis-lab.de/Opamp59.htm (https://www.richis-lab.de/Opamp59.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on October 06, 2022, 06:27:36 am
Okay, but how it works? ;)

Refering to 62x03.jpg, I think the red areas are polysilicon, and the output transistors filled with red are MOSFETs. Most other transistors seem to be BJT, then.

The inputs are clamped differentially with diodes and routed to what must be a BJT diff pair, because of high bias current. The collectors go towards resistors to ground and emitters of fairly typical vertical BJTs; this looks like NPN folded cascode, so the input pair is PNP. The collectors of the NPNs go to a 3-PNP Wilson mirror degenerated by the laser-trimmed resistors. (The fourth PNP in this area is the tail current source). That's the input stage, which was easy to find because of the trimmed resistors and the input pins.

Maybe there is some second stage or not, and then the output stage. I will have to take a closer look.
Title: Re: Opamps - Die pictures
Post by: Noopy on October 06, 2022, 07:19:37 am
Okay, but how it works? ;)

Would be interesting!  ;)


Refering to 62x03.jpg, I think the red areas are polysilicon, and the output transistors filled with red are MOSFETs. Most other transistors seem to be BJT, then.

I agree with you, most is BJT and the output transistors are MOSFETs.  :-+


The inputs are clamped differentially with diodes and routed to what must be a BJT diff pair, because of high bias current. The collectors go towards resistors to ground and emitters of fairly typical vertical BJTs; this looks like NPN folded cascode, so the input pair is PNP. The collectors of the NPNs go to a 3-PNP Wilson mirror degenerated by the laser-trimmed resistors. (The fourth PNP in this area is the tail current source). That's the input stage, which was easy to find because of the trimmed resistors and the input pins.

Maybe there is some second stage or not, and then the output stage. I will have to take a closer look.

 :-+ :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on October 07, 2022, 07:54:00 am
(https://www.richis-lab.de/images/Opamp/62x05.jpg)

Now I know what the green area is!
In the first overview picture in the first post you can see that there are broad vertical stripes under the green surface. I somehow didn´t recognize these stripes...
Now it makes much more sense. That is a serial connection of some J-FETs. The green area is the big common gate.  :-+
Title: Re: Opamps - Die pictures
Post by: sansan on October 07, 2022, 08:48:24 am
:blah:

@Noopy, please compare NS/TI's vs UTC's LM1875 die?  ;D
Title: Re: Opamps - Die pictures
Post by: Noopy on October 07, 2022, 11:49:55 am
:blah:

@Noopy, please compare NS/TI's vs UTC's LM1875 die?  ;D

I can do that but it will take some time... :)
Title: Re: Opamps - Die pictures
Post by: sansan on October 07, 2022, 03:20:04 pm
I can do that but it will take some time... :)
Thankyou..

LM1875 was a well-known NatSemi /(and later) TI's product. But UTC also sells LM1875 under thier name "LM1875L". Their datasheet also seems similar.
I think some DIYers say they sound a bit different (some modification in the die, they assume).
Kit-Amp.com compare their die size, they are the same size (& did not reveal any sound difference, they say).
http://kit-amp.com/lm1875-fake-original (http://kit-amp.com/lm1875-fake-original)

I've emailed TI & UTC, whether the UTCs LM1875 has the same crystal (i.e original), neither of them gave me a "clear" answer.

Peeking at the die should dispel that myth... I suppose  ;D ;D ;D :horse: ;D


UTC also sells TDA2050, some say the old ST ones has more robust protection.
Title: Re: Opamps - Die pictures
Post by: magic on October 07, 2022, 04:49:15 pm
Now I know what the green area is!
In the first overview picture in the first post you can see that there are broad vertical stripes under the green surface. I somehow didn´t recognize these stripes...
Now it makes much more sense. That is a serial connection of some J-FETs. The green area is the big common gate.  :-+
Makes sense. If these aren't JFETs, they must be MOSFETs, because the bias generator requires a current sink here to work.

It seems that my identification of transistor types was correct too, because the whole circuit makes sense this way.

(https://www.eevblog.com/forum/projects/opamps-die-pictures/?action=dlattach;attach=1608886;image)

Continuing where I left off, emitter followers Q8,Q9 bootstrap the current mirror to follow its own output voltage. This causes Q3 and Q4 collector voltages to be approximately equal and to track output swings, so Early effect in Q4 is cancelled differentially by Q3 and the mirror. This boosts output impedance of the input stage and this stage likely accounts for most of the unusually high (for such a simple low power chip) open loop gain. Some high performance bipolar opamps like AD797 and LT1469 generate all their gain with this kind of input stage, followed by a unity gain buffer with lots of current gain (therefore high input impedance). Scott Wurcer from Analog published a whole article about the 797 and its design.

Unity gain and rail to rail doesn't come together easily, so here there is a complementary common source MOSFET output stage instead, which has some additional gain (inverting, of course) and full output swing. The input stage drives the output NMOS directly, although the connection isn't immediately obvious, passing through several long traces and the gate of M4. A MOSFET gate is basically open circuit, so the high impedance of the input stage isn't loaded much by the output stage, at least near DC. C1 implements Miller frequency compensation.

D1,D2,M1,M2 is a sort of current mirror, but no current can flow through M2 unless M3 and M4 sink it. I don't know exactly how the combination of M3,M4 is supposed to behave, but I think we can agree that it sinks more current when the gate voltage goes up and stops sinking when it goes down ::) This current is mirrored by D2,Q10 and works against I5, driving the output PMOS. To keep the PMOS gate constant, some current must flow from M4 to cancel I5, therefore some idle bias is preserved in the output NMOS M5.

Since M6 gate is a high impedance load, this circuit has some gain too (gate voltage swing is larger at M6 than at M5). It seems that C2 loads down this "amplifier" to reduce its gain at high frequencies and avoid some stability problems that apparently occurred otherwise.

Then there is some gate zeners and current limiting and stuff. Q13 seems to turn off the PMOS when the NMOS enters current limiting, or something like that.

I didn't bother drawing all those biasing current mirrors completely. The proportions of transistor areas and resistors look a little odd; I suspect there is some black magic there, that produces different thermal coefficients in different current sources to achieve different goals, or whatever.
Title: Re: Opamps - Die pictures
Post by: Noopy on October 07, 2022, 06:39:12 pm
Well done!  :-+

Would it be ok for you if I put your schematic on my website?
Title: Re: Opamps - Die pictures
Post by: magic on October 07, 2022, 06:54:08 pm
Yeah, you can post it.
I doubt anyone cares, anyway :-DD

Check if I haven't made some stupid mistakes.
I noticed that I forgot about the differential input clamp. By the way, I'm not 100% sure how it works, there is very few connections to those NPNs(?), not like the usual antiparallel diodes configuration. Maybe they only use the CB or BE junctions, perhaps as zeners? Hard to tell from these images...

And I forgot to mention something about the PNPs. The outermost connection is the collector, not the base, so it looks like they are vertical rather than lateral PNPs. The NPNs definitely look like typical vertical NPNs too, so it could be a more or less complementary process. Plus CMOS. Honestly, all that BiCMOS stuff is alien technology to me.

And dielectric isolation with fused wafers? Is this an expensive chip, like OPA627-level expensive?
Title: Re: Opamps - Die pictures
Post by: magic on October 07, 2022, 07:02:03 pm
I think some DIYers say they sound a bit different (some modification in the die, they assume).
Kit-Amp.com compare their die size, they are the same size (& did not reveal any sound difference, they say).
http://kit-amp.com/lm1875-fake-original (http://kit-amp.com/lm1875-fake-original)
These guys are amateurs, they need more flames >:D
https://www.eevblog.com/forum/projects/decapping-and-chip-documentation-howto/ (https://www.eevblog.com/forum/projects/decapping-and-chip-documentation-howto/)

You could do it yourself if you have a few of those chips to spare. But photographing is harder, there is no widely available and cheap consumer equipment capable of really high resolution, only expensive equipment or modding.

I've emailed TI & UTC, whether the UTCs LM1875 has the same crystal (i.e original), neither of them gave me a "clear" answer.
Post the responses you did receive, I want a laugh ;D
Title: Re: Opamps - Die pictures
Post by: sansan on October 07, 2022, 07:55:10 pm
These guys are amateurs, they need more flames >:D
https://www.eevblog.com/forum/projects/decapping-and-chip-documentation-howto/ (https://www.eevblog.com/forum/projects/decapping-and-chip-documentation-howto/)

You could do it yourself if you have a few of those chips to spare. But photographing is harder, there is no widely available and cheap consumer equipment capable of really high resolution, only expensive equipment or modding.
I've seen a guy on YT decapping PDIP using nitric acid & heat (hotplate or something, I forgot). And acetone for cleansing. Quite clean result I think, but no macro(micro?) photos if I recall correctly.
The DIY Oven at post#3 is very noice  :-+  :popcorn:

Post the responses you did receive, I want a laugh ;D
to put it simply, they tell me to compare the datasheit   |O :wtf: :horse: :horse:

Ah, HGsemi also sells LM1875...  :scared:
http://www.hgsemi.net/en/goods/list-80.html (http://www.hgsemi.net/en/goods/list-80.html)
Title: Re: Opamps - Die pictures
Post by: Noopy on October 08, 2022, 06:22:28 am
And I forgot to mention something about the PNPs. The outermost connection is the collector, not the base, so it looks like they are vertical rather than lateral PNPs. The NPNs definitely look like typical vertical NPNs too, so it could be a more or less complementary process. Plus CMOS. Honestly, all that BiCMOS stuff is alien technology to me.

And dielectric isolation with fused wafers? Is this an expensive chip, like OPA627-level expensive?

This CBCMOS process seems to be a expensive one like the OPA627 process, yes. Perhaps it´s even more expensive since it is important to grind the upper silicon to a level the n+/n/n+ channel is normally-off.
I assume this process also makes it easier to produce vertical PNPs.

Regarding the input protection: Yes, this structure looks strange. With the special process they used they probably were able to generate quite different protection structures compared to a normal bipolar process.


These guys are amateurs, they need more flames >:D
https://www.eevblog.com/forum/projects/decapping-and-chip-documentation-howto/ (https://www.eevblog.com/forum/projects/decapping-and-chip-documentation-howto/)

You could do it yourself if you have a few of those chips to spare. But photographing is harder, there is no widely available and cheap consumer equipment capable of really high resolution, only expensive equipment or modding.
I've seen a guy on YT decapping PDIP using nitric acid & heat (hotplate or something, I forgot). And acetone for cleansing. Quite clean result I think, but no macro(micro?) photos if I recall correctly.
The DIY Oven at post#3 is very noice  :-+  :popcorn:

Works fast and well and is a little more healthy than hot concentrated nitric adic.  :o
Title: Re: Opamps - Die pictures
Post by: mawyatt on October 08, 2022, 03:28:51 pm
And I forgot to mention something about the PNPs. The outermost connection is the collector, not the base, so it looks like they are vertical rather than lateral PNPs. The NPNs definitely look like typical vertical NPNs too, so it could be a more or less complementary process. Plus CMOS. Honestly, all that BiCMOS stuff is alien technology to me.

And dielectric isolation with fused wafers? Is this an expensive chip, like OPA627-level expensive?

This CBCMOS process seems to be a expensive one like the OPA627 process, yes. Perhaps it´s even more expensive since it is important to grind the upper silicon to a level the n+/n/n+ channel is normally-off.
I assume this process also makes it easier to produce vertical PNPs.

Regarding the input protection: Yes, this structure looks strange. With the special process they used they probably were able to generate quite different protection structures compared to a normal bipolar process.


Yes the bonded wafer technique also like Harris had with their UHF1 & 2 processes is expensive.

Best,
Title: Re: Opamps - Die pictures
Post by: sansan on October 27, 2022, 08:52:35 am
Noopy, what is the bond wire usually made of?
pure gold or a gold plated copper? ora maybe other materials?
Title: Re: Opamps - Die pictures
Post by: Noopy on October 27, 2022, 08:55:45 am
First is was gold or aluminium, today you have also copper and paladium coated copper. If the copper is paladium coated you don't need inert gas for bonding.
Title: Re: Opamps - Die pictures
Post by: sansan on October 27, 2022, 09:02:56 am
First is was gold or aluminium, today you have also copper and paladium coated copper. If the copper is paladium coated you don't need inert gas for bonding.
What do you mean by "first"? Like, first grade (as for super fine precision Op Amps)...

or "first" like old chips (its age/generation)..? because now gold is very expensive  :bullshit: ;D
Title: Re: Opamps - Die pictures
Post by: Noopy on October 27, 2022, 09:13:32 am
The old chips used gold but you still use it today. Gold is very stable. If you use copper you for example have to double check the mould compound for compatibility.
Title: Re: Opamps - Die pictures
Post by: sansan on October 27, 2022, 09:29:52 am
technical term just got beyond my brain capability.. ;D |O
mould compound? that square-black resin thing?
so if the compound not compatible, it might make the copper bond wire to oxidize or some kind? wow

As for aluminum bond wire, it must have been used for uA741... ;D ;D ;D

Danke Noopy, very useful information.  :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on October 27, 2022, 09:41:25 am
Yes, mould comes from moulding. Mould compound is the black potting stuff. Copper is very unstable (especially compared to gold) if you have the wrong substances around it turns into a mess.  >:D

The potting is more sophisticated than most people think. It has to have a texture that you can inject it around the chip without killing the bondwires. Once hardened it has to protect the bondwires (chemically and mechanically). It has to be as tight as possible (especially around the metal pins). It has to withstand "normal" temperature changes and reflow temperatures. It has to be "black", so no light comes through. Today it should be as "green" as possible. And of course, cost is a important point too.
Just a small blink...

 :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on November 20, 2022, 07:19:58 pm
(https://www.richis-lab.de/images/Opamp/63x01.jpg)

The TL06x family is the low power variant of the TL08x opamps. The TL08x series was introduced by Texas Instruments in 1977 and were named BIFET opamps. TI integrated the JFET input transistors into the manufacturing process and thus onto the die. JFETs could be integrated into normal bipolar processes even before that, but these JEFTs are not suitable as input transistors of an operational amplifier because of their poor specifications.

As with the TL08x, the TL06x offer several variants. The TL061 is a simple, internally compensated opamp. The TL060 lacks the internal compensation capacitor and its bandwidth must be limited externally. The TL062 offers two opamps, but lacks the connections for external offset compensation. In the TL064 there are four opamps.

The index C marks the opamps which are released for a temperature range between 0°C and 70°C. The best variant M, on the other hand, allows operating temperatures between 0°C and 70°C. The best variant M, on the other hand, allows operating temperatures between -55°C and 125°C. The TL062 is designed for a summetrical supply voltage between +/-5V and +/-15V. With the JFETs they were able to specify the bias current of the inputs to typically 30pA, maximum 400pA. Over the full operating temperature range one has to expect up to 10nA. Offset voltage ranges from 3mV to 20mV with a typical temperature drift of 10µV/°C. The cutoff frequency is specified as 1MHz, the maximum slew rate is 3,5V/µs.


(https://www.richis-lab.de/images/Opamp/63x02.jpg)

The schematic shown here is taken from the Texas Instruments datasheet. The individual blocks are colored. At the input is the differential amplifier built with JFETs (yellow). The biasing (blue/cyan) is based on a relatively complex reference current generation. While the voltage amplifier stage is supplied by a simple current mirror, there are two transistors (cyan) above the differential amplifier. This seems to be kind of a cascode, which shields the differential amplifier better from supply voltage fluctuations.

The differential amplifier at the input is followed by the voltage amplifier stage (green), which also serves as a driver for the output transistors. The output stage (red) is constructed with one NPN and one PNP transistor. A Vbe multiplier (gray) generates the voltage between the output transistors, which is necessary to achieve an optimal quiescent current and to minimize the distortions in the zero crossing.

The highside transistor has a direct acting overcurrent protection (dark red). If too high a current flows across the 50Ω resistor, the transistor placed above it sinks the base current of the highside transistor. The lowside transistor is only rudimentarily protected with a 100Ω emitter resistor. An additional protection stage is located in the voltage amplifier stage (dark green). If the drive current of the lowside transistor increases too much, the driver current of the voltage amplifier stage is reduced.


(https://www.richis-lab.de/images/Opamp/63x03.jpg)

(https://www.richis-lab.de/images/Opamp/63x04.jpg)

The dimensions of the die are 1,5mm x 1,4mm. The largest part of the area is taken up by the input transistors and the compensation capacitors. On the die, next to some TI logos, the designation TL062B is shown. The B could stand for a second revision.


(https://www.richis-lab.de/images/Opamp/63x05.jpg)

(https://www.richis-lab.de/images/Opamp/63x06.jpg)

The two input transistors are divided into two transistors each and cross-connected so that temperature gradients affect both branches of the differential amplifier as equally as possible.

The JFETs are clearly unbalanced. A V-shaped gate electrode separates each two drain areas from a common source area.


https://www.richis-lab.de/Opamp60.htm (https://www.richis-lab.de/Opamp60.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Kleinstein on November 20, 2022, 09:39:27 pm
I think drain and source are swaped with the JFETs. This are P-channel and thus source at the more positive side.
So the small single contacts would be source.

I just noticed that the ST data-sheet for the TL062 also allow for +-2 V supply operation.
I somehow rememeber seeing the TL06x quite a bit in circuits powered from a single 9 V battery - slighlt less than +-5 V recommended by Ti.

The extra Transistor in the current source is not just for supply variations, but also for better common mode rejection.

AFAIk the current limitation for the negative side uses the rather limit gain of the PNP transistor combined with the current limit in the voltage amplifier stage.
Title: Re: Opamps - Die pictures
Post by: Noopy on November 20, 2022, 09:52:07 pm
I keep doing the same mistake!  |O
Thanks for the hint.  :-+ I have updated my website und due to hotlinking the picture here should be updated soon too.

Interesting that ST needs less supply voltage...

Indeed, the additional transistor is good for CMMR too.  :-+
Title: Re: Opamps - Die pictures
Post by: magic on November 21, 2022, 09:15:10 am
National was first to this game with their LF156 and BiFET was National's marketing name, not TI's ;)

Not sure how you guys got ±2V operation, current ST datasheet specifies operating voltage range of 6V to 36V. Only some typical characteristics are given down to 4V and it looks like the chip will bias up and sort of work, but it's unclear if much useful common mode input range will be available. The same plots are in TI datasheet too, despite the ±5V spec.

Notably missing from both vendors is CMIR vs VCC |O

edit
People sometimes worry about bias current mirrors being shared between channels of dual opamps and unwanted disruptions when one channel's input or output saturates to the wrong rail. It seems to be very uncommon in practice, but we have an example here in all those PNPs surrounding the VCC pad, thank you TI ::)
Title: Re: Opamps - Die pictures
Post by: Noopy on November 21, 2022, 09:25:39 am
TI called it BIFET too!
I never said they TI were the first / only one.  ;)
Title: Re: Opamps - Die pictures
Post by: magic on November 21, 2022, 09:27:27 am
Well, I think you said they were first.

TI integrated the JFET input transistors into the manufacturing process and thus onto the die. JFETs could be integrated into normal bipolar processes even before that, but these JEFTs are not suitable as input transistors of an operational amplifier because of their poor specifications.

Besides, it didn't stop people from trying. We have already seen chips with specs like ±20mV offset voltage ;D

edit
I checked a few TI datasheets and couldn't find any mention of "BiFET". It's always described as "JFET input operational amplifier", until they changed it recently to "FET input" in order to smuggle a new CMOS product into the series.
Title: Re: Opamps - Die pictures
Post by: Noopy on November 21, 2022, 09:32:36 am
Now I see your point!
I blame it on my english skills. ;D
I thought of TI which had no (good) possibility to use JFETs in the input stage until they introduced the BIFET process.


Well, I think you said they were first.

TI integrated the JFET input transistors into the manufacturing process and thus onto the die. JFETs could be integrated into normal bipolar processes even before that, but these JEFTs are not suitable as input transistors of an operational amplifier because of their poor specifications.

Besides, it didn't stop people from trying. I remember specs like ±20mV offset voltage ;D
Title: Re: Opamps - Die pictures
Post by: David Hess on November 24, 2022, 03:04:56 pm
People sometimes worry about bias current mirrors being shared between channels of dual opamps and unwanted disruptions when one channel's input or output saturates to the wrong rail. It seems to be very uncommon in practice, but we have an example here in all those PNPs surrounding the VCC pad, thank you TI ::)

Specific older parts have that problem, and even some new designs to one extent or another.  Check page 10 of the Linear Technology LT1013/LT1014 datasheet (https://www.analog.com/media/en/technical-documentation/data-sheets/lt1013-lt1014.pdf) for an example:

There is one circumstance, however, under which the phase reversal protection circuitry does not function: when the other op amp on the LT1013, or one specific amplifier of the other three on the LT1014, is driven hard into negative saturation at the output.

Phase reversal protection does not work on amplifier:

A when D’s output is in negative saturation. B’s and C’s outputs have no effect.
B when C’s output is in negative saturation. A’s and D’s outputs have no effect.
C when B’s output is in negative saturation. A’s and D’s outputs have no effect.
D when A’s output is in negative saturation. B’s and C’s outputs have no effect.

Title: Re: Opamps - Die pictures
Post by: Noopy on December 23, 2022, 06:45:49 pm
(https://www.richis-lab.de/images/Opamp/64x01.jpg)

The AD549 is a so-called electrometer opamp. These are opamps with extremely low input currents. In the best bin with index L, the typical input current is just 40fA regardless of the common mode voltage. This corresponds to just one electron every four microseconds. Up to the maximum operating temperature of 70°C this current rises sharply as usual, but remains below 2,8pA.

The typical offset voltage is 0,3mV and can increase up to 0,9mV at high temperatures. The bandwidth is 1MHz, the slew rate 3V/µs.


(https://www.richis-lab.de/images/Opamp/64x03.jpg)

A 1992 Analog Devices advertisement compares the AD549's specifications to other low-noise op amps. The bias current of the AD549 stands out especially. It is by far the lowest of all types.


(https://www.richis-lab.de/images/Opamp/64x11.jpg)

Analog Devices achieves the extremely low input current with the so-called "Topgate JFET Technology". The datasheet refers to the patent US5319227 "Low-leakage JFET having increased top gate doping concentration". This patent describes a special JFET and contains the above figure, which has been colored here for better understanding.

Much of the leakage current of an ordinary JFET occurs at the large interface between the gate and the substrate. In the top-gate JFET described in the patent, the upper part of the gate is isolated from the lower part. As will be shown, the input signal of the AD549 is connected only to the upper part of the gate. The small area and isolation from the substrate significantly reduces leakage current.


(https://www.richis-lab.de/images/Opamp/64x06.jpg)

(https://www.richis-lab.de/images/Opamp/64x05.jpg)

The package provides a guard pin that is only connected to the housing. If you do not want to increase the low input currents of the AD549 excessively by leakage currents, you have to surround the input potentials with shields which carry the same potential. This applies to the housing but also and especially to the circuit board. It is even better not to build the critical input pin with the input circuitry on the board at all, but to construct it on highly insulating spacers.

The negative supply potential is led to the die with two bondwires.


(https://www.richis-lab.de/images/Opamp/64x07.jpg)

(https://www.richis-lab.de/images/Opamp/64x08.jpg)

Since the guard potential is applied to the housing, the die must be isolated from the housing with a ceramic carrier.


(https://www.richis-lab.de/images/Opamp/64x02.jpg)

Older versions of the datasheet contain an image of the metal layer. The dimensions of the die are therefore 2,06mm x 1,905mm.


(https://www.richis-lab.de/images/Opamp/64x10.jpg)

(https://www.richis-lab.de/images/Opamp/64x09.jpg)

On the die there is the designation 549 and twice two letters that could be abbreviations of the developers. The design dates back to 1985.

Several resistors were calibrated with a laser. Typical for Analog Devices, there is a square with a testpad on the lower edge that is used to adjust the laser process and the number 1 is engraved in the upper right corner.


(https://www.richis-lab.de/images/Opamp/64x12.jpg)

The datasheet of the AD549 does not contain a circuit diagram. However, it refers to the patent US4639683, which describes the above opamp. As will be shown, the schematic shown there matches the circuit in the AD549 except for one small detail. For better understanding, the individual function blocks have been colored.

The red block is the differential amplifier at the input of the OP549. The JFETs J6/J7 are the input transistors. They each have two gate terminals, of which just the top gate is connected to the respective input. The differential amplifier has its own V- potential. The double transistor Q21 guarantees that the potentials in this part of the circuit never rise too high. The transistors Q18/Q19 represent a current mirror with which the input transistors operate. Q17 generates the base current of the current mirror. Transistor Q23 forms the output of the differential amplifier with current sink Q22. Current sink Q20 appears to have been inserted in the left path to keep the circuit as symmetrical as possible.

Transistors Q15/Q16 probably reduce saturation effects when the input stage is overdriven. In this case, they open the cascode transistors J8/J9 (cyan), which otherwise shield the input transistors from the effects of common mode voltages.

The bias setting (blue) is relatively complex. It is based on the two JFETs J1A and J1B with resistor R1. The reference current generated across them is distributed to the circuit parts under J3 and J5 by transistor Q1. The cascode circuit with the JFETs isolates the current sources from voltage fluctuations. The reference current is further multiplied in the lower half by transistors Q3-Q6 and Q9-Q12.

Resistor R2A is balanced so that, in combination with the reference current, the same potential is present at testpad 30 as at the front gates of J6 and J7. Via transistors Q8/Q13/Q14 (green) this potential is transferred to the respective back gates. This ensures that front gate and back gate always have the same potential.

The input amplifier controls the voltage amplifier stage (yellow), which in turn controls the output stage (gray). The quiescent current setting (purple) reduces the crossover distortion. The power amplifier is supplied by its own current mirror consisting of Q7 and J10. Q30 and Q31 protect the output stage from too high currents. An overcurrent on the lowside does not directly reduce its output level, but the drive of the voltage amplifier stage.

An important point of the circuit is the adjustment. First, using resistor R1, the current through J1A/J1B is set to the value at which the temperature coefficient of the JFETs becomes minimum. Then R2A is adjusted so that the potential at point 30 is the same as at the front gates, i.e. the inputs of the AD549. This is necessary to get the same potential at the back-gates as at the front-gates. The JFETs J1A/J1B are constructed in the same way as the input transistors J6/J7. This ensures that production variations and drift effects affect both transistor pairs very similarly.

After the adjustment of the bias, the offset voltage and temperature drift of the input stage are adjusted. The resistors R5/R6 define the distribution of the currents to the two input transistors. Since the temperature drift of the JFETs depends on the drain current, the temperature drift of the offset voltage can be adjusted via this resistors. For this reason, it is not ideal for a JFET differential amplifier to adjust the offset voltage via the ratio of the drain currents, since this simultaneously changes the temperature drift of the offset voltage. Instead, the offset voltage of the AD549 is adjusted with the source resistors R2B/R2C. Because there is no easy way to vary the source resistors externally, the external offset adjustment is still done via the current distribution in the two branches. Accordingly, the datasheet indicates an additional temperature drift of up to 2,4µV/°C per adjusted millivolt of offset voltage.


(https://www.richis-lab.de/images/Opamp/64x13.jpg)

On the die all components from the schematic of the patent can be found. Just the resistor RJ9 is a small deviation. This resistor is located in the drain connection of the cascode JFET J9. It is from this branch of the differential amplifier that the signal is decoupled to the voltage amplifier stage. The resistor was obviously inserted quite deliberately. The purpose of the resistor remains unclear.


(https://www.richis-lab.de/images/Opamp/64x04.jpg)

The JFETs in the input amplifier of the AD549 are located in the center (red). Directly next to them, the JFETs of the reference path are integrated (blue). The arrangement around the horizontal symmetry axis of the die reduces the effects of thermal gradients, which are generated to a large extent by the output stage (gray). There, the lowside transistor has been split into two transistors and arranged around the highside transistor. This measure guarantees that independent of the load of highside and lowside the power dissipation always occurs symmetrically around the horizontal symmetry axis of the die. The remaining critical transistors of the input amplifier are arranged on the symmetry axis too (yellow).


(https://www.richis-lab.de/images/Opamp/64x14.jpg)

The two JFETs at the input of the differential amplifier and the two JFETs in the reference path are integrated so that they behave as equally as possible. A further improvement could only be achieved by splitting and cross-connecting the transistors, but this would increase the area of the input transistors too, which would then again have a negative effect on the leakage currents and parasitic capacitances.

Having the operating current of the JFETs set by identical JFETs is extremely advantageous. David Fullagar describes in the widely cited article "Better understanding of FET operation yields viable monolithic J-FET op amp" that production variations cause the drain current Idss of integrated JFETs to drift by a factor of 9. Accordingly, it is difficult to define an ideal operating current in a design.


(https://www.richis-lab.de/images/Opamp/64x15.jpg)

If you compare the structures with the patent US5319227, the parallels are easy to see. Just the source contact is not on the outside in the AD549, but between the top-gate and the back-gate connection.


(https://www.richis-lab.de/images/Opamp/64x16.jpg)

(https://www.richis-lab.de/images/Opamp/64x17.jpg)

The structures cannot be immediately assigned at first glance. This is mainly due to the fact that the colors on the die are partly inverse to the usual colors for n- and p-doping.

The outermost square frame is the boundary between the n-doped well and the heavily p-doped insulating layer surrounding the transistor. The n-doped well carries the potential of the back gate.

The dark blue frame contains the strong p-doping, which is the larger, outer source electrode. Below the center drain contact is the same doping, but it is hidden by the metal layer.

The red area is the n-doped top gate. Below it is the channel between source and drain. At the transitions from the red gate area to source and drain, a kind of frame can be seen. Probably there the gate area overlaps the highly doped contacts to the actual channel. So you can be sure that the channel is completely covered by the gate.

The buried layer with its strong n-doping, which is used as a collector feed line in NPN transistors, is just visible as a step in the surface.


(https://www.richis-lab.de/images/Opamp/64x18.jpg)

The two lines from the inputs of the AD549 to the JFETs of the differential amplifier (red) are shielded with the potentials of the back-gates (green). This reduces the parasitic capacitances and probably also the leakage currents to some extent.


(https://www.richis-lab.de/images/Opamp/64x20.jpg)

Resistors R1 and R2A each consist of two elements that allow more extensive adjustment. A test point allows to measure the potential above resistor R2, which is necessary to adjust the synchronization of reference current source and input stage.


(https://www.richis-lab.de/images/Opamp/64x21.jpg)

The resistors R5/R6, which are used to adjust the offset drift, provide a less complex structure. The traces of the adjustment are clearly visible.

The design offers the possibility to increase the capacitor Cc and thus adjust the frequency response.


(https://www.richis-lab.de/images/Opamp/64x19.jpg)

The bipolar transistors Q15 and Q18 are directly integrated into the structures of the JFETs J9 and J8.


https://www.richis-lab.de/Opamp61.htm (https://www.richis-lab.de/Opamp61.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Gyro on December 23, 2022, 08:19:08 pm
While you're on very low input current opamps, it would be interesting to see the LMC662, it has a typical 25'C input current of 3fA and is cheap. There has been some discussion here as to whether its input protection networks are bootstrapped or not.

You tend to find them scattered liberally in the high impedance sections of commercial picoammeter and SMU type products, eg. https://www.eevblog.com/forum/metrology/project-for-standalone-use-of-keithley-low-current-preamplifier/ (https://www.eevblog.com/forum/metrology/project-for-standalone-use-of-keithley-low-current-preamplifier/)
Title: Re: Opamps - Die pictures
Post by: Noopy on December 23, 2022, 08:24:54 pm
Yesterday I have put the LMC662 on my ToDo list.  :-+
3fA is really "enormous".  8)
Title: Re: Opamps - Die pictures
Post by: David Hess on December 24, 2022, 02:40:21 am
Yesterday I have put the LMC662 on my ToDo list.  :-+
3fA is really "enormous".  8)

The LMC6041/2/4, LMC6061/2/4, and LMC6081/2/4 all use the same design with associated 3 femtoamp input current, so should be just as good for analysis.
Title: Re: Opamps - Die pictures
Post by: Noopy on December 24, 2022, 05:30:01 am
Yesterday I have put the LMC662 on my ToDo list.  :-+
3fA is really "enormous".  8)

The LMC6041/2/4, LMC6061/2/4, and LMC6081/2/4 all use the same design with associated 3 femtoamp input current, so should be just as good for analysis.

That is good to know! Thanks for the hint.  :-+

First I wanted to wait for the next Mouser order but that would have taken some time so I ordered a ceramic LMC662 from GB. Not the cheapest way to get one but without epoxy the pictures often get better and it is less messy.  ;D

I think I will fast forward the LMC662. He deserves it.  :-/O
Title: Re: Opamps - Die pictures
Post by: RoGeorge on December 24, 2022, 10:28:09 am
Quote
half connected LMC662 - TI LMC6001
https://zeptobars.com/en/read/Ti-LMC6001-25fA-input-current (https://zeptobars.com/en/read/Ti-LMC6001-25fA-input-current)

I have a saved html page with that pic saved in 2018 from ZeptoBars, so LMC6001 might also have the same die as LMC662.  Not sure where from I got the info, or if that is correct, on the die it is written LMC6001.  :-//

Would be interesting to check.




Was saving bits of info about LMC662 because I've seen a video with a big food can where the lid of the can was cut smaller, then the lid was glued in perpendicularly on a rod.  The lid was dived near the bottom of the can, without touching the can, so the can-body + lid were forming a parallel plates air capacitor.  On this capacitor there was the input of a LMC662 voltage follower.  (note the upper left capacitor with arrows suggesting variable distance between plates, that's the can+lid glued on a rod).

Then, the operator was charging the capacitor from a 9V battery, then remove the battery.  The fun part was that the charge on the lid+can capacitor was conserved, while the LMC662 follower was displaying the plates voltage (with a voltmeter improvised from an analog uA-meter and a resistor).

The input bias was so small that one could clearly see how the plates voltage was going up and down repeatedly, proportional with the distance between the plates, while the distance was changed by pulling the rod up and down.  ^-^
Title: Re: Opamps - Die pictures
Post by: magic on December 24, 2022, 10:45:43 am
Picture linked from ZeptoBars.com
Can we have some reasonable limits on the size and dimensions of images that get directly inlined here?
That's 37 mega friggin' bytes and a 6k image that you have just forced every viewer of this thread to download and display :rant:

I seem to recall that there is a video interview with Bob Pease somewhere where he says that the 6001 was derived from the 662.
The 6001 chip is obviously some dual opamp turned into single by metal layer change.
Title: Re: Opamps - Die pictures
Post by: Noopy on December 24, 2022, 11:14:16 am
We will have to take a look to be sure!  :-/O ;D
Title: Re: Opamps - Die pictures
Post by: RoGeorge on December 24, 2022, 11:44:47 am
Picture linked from ZeptoBars.com
That's 37 mega

I apologize, didn't realize it's that big.  Picture hotlink removed.
(side effect of having obscene Internet at 760Mbps download)
Title: Re: Opamps - Die pictures
Post by: magic on December 24, 2022, 12:55:04 pm
Sorry for the rant, but this image went far beyond even the usual horrors of the "beginners" section :P
Besides, inlining images with such resolution is nuts IMVHO - either it's unscaled and it blows up the size of the page or it gets scaled and you can't see all that detail anyway.
For any sensible use it has to be opened it a separate tab, unless you have a high DPI monitor the size of a wall.

And going back to LMC660/662, there may or may not have been two revisions of those chips, because early datasheets (like 1989) showed 40fA typical.
OTOH, in the same interview, Pease said that simply improving the test setup had enabled them to measure it more accurately and give better specs, so it's not clear if any silicon tweak took place.
The only way to know for sure would be opening early and later production chips ::)
Title: Re: Opamps - Die pictures
Post by: Noopy on December 24, 2022, 01:06:25 pm
We will have to take a look to be sure!  :-/O ;D

 ;D
Title: Re: Opamps - Die pictures
Post by: David Hess on December 24, 2022, 02:31:12 pm
I have a saved html page with that pic saved in 2018 from ZeptoBars, so LMC6001 might also have the same die as LMC662.  Not sure where from I got the info, or if that is correct, on the die it is written LMC6001.  :-//

The LMC6001 is an LMC6081 tested for its low input bias current.  They are otherwise the same chip.  The "typical" input bias current for the LMC6081 is just a couple femtoamps, but it is not tested to this level because of the extra cost for testing.  I have never seen an LM6081 with an input bias current higher than 5 femtoamps.

I assume that there is a layout difference between the LMC662 and LMC6042/LMC6062/LMC6082 which allows the later to be "precision" parts, but that I do not know.  Maybe the later use thermally coupled quads and the LMC662 did not?
Title: Re: Opamps - Die pictures
Post by: magic on December 24, 2022, 03:18:55 pm
These two may save some people some time ;)
Not gonna bother rewatching the whole video, you guys tell me what interesting was there.

https://youtu.be/B4G3YPlO6Wg (https://youtu.be/B4G3YPlO6Wg)
http://class.ece.iastate.edu/djchen/EE501/2011/MonticelliRailToRailOutSwing.pdf (http://class.ece.iastate.edu/djchen/EE501/2011/MonticelliRailToRailOutSwing.pdf)
Title: Re: Opamps - Die pictures
Post by: iMo on December 24, 2022, 03:37:52 pm
Do you have a modern opamp chopper picture too?
Title: Re: Opamps - Die pictures
Post by: Noopy on December 24, 2022, 03:52:25 pm
Do you have a modern opamp chopper picture too?

Not right now but I have it on my ToDo list.  ;D
Title: Re: Opamps - Die pictures
Post by: Noopy on December 27, 2022, 04:13:52 am
[...]
Not gonna bother rewatching the whole video, you guys tell me what interesting was there.

https://youtu.be/B4G3YPlO6Wg (https://youtu.be/B4G3YPlO6Wg)
[...]

Roundup: It´s not easy to measure very small currents.  ;D
I didn´t find very much additional information about the 662/6001. For me it sounded like 6001 is a further development of the 662 but is not really based on the design of the 662. We will see...
Title: Re: Opamps - Die pictures
Post by: David Hess on December 27, 2022, 07:03:05 am
Pease also discussed the development of the test circuits in his Pease Porridge column, although he never mentioned the exact application.  Resetting the integration capacitor without excessive charge injection was a challenge.  He also started with an air capacitor, but the large volume picked up too many cosmic rays until it was replaced with a smaller Teflon capacitor.

Title: Re: Opamps - Die pictures
Post by: Noopy on January 20, 2023, 07:34:02 pm
(https://www.richis-lab.de/images/Opamp/65x01.jpg)

You wanted to see the LMC662? Well, here it is!  8)

The LMC662 is a dual operational amplifier with respectable specifications. The LMC662AMJ variant here is approved for a temperature range of -55°C to +125°C. As will become apparent, the LMC662 is based on the LMC660 quad operational amplifier.

The LMC662 needs just a single supply between 5V and 15V. The current consumption is less than 0,75mA. The input voltage range includes the negative supply. The output is rail to rail. Depending on the operating point, the output stage allows currents up to 40mA. With a slewrate of 1,1V/µs, the LMC662 achieves a cutoff frequency of 1,4MHz.

The extremely low bias current of typically 2fA is achieved by a CMOS input stage. Nevertheless, the noise voltage is quite low at 22nV/√Hz. The current noise is 0,2fA/√Hz. The offset voltage is typically 1mV with a temperature drift of 1,3µV/°C.


(https://www.richis-lab.de/images/Opamp/65x02.jpg)

In the datasheet of the LMC662, National Semiconductor shows the somewhat unusual structure of the LMC662. The differential amplifier at the input is followed by a voltage amplifier stage consisting of a non-inverting and an inverting amplifier. Above this voltage amplifier stage is the compensation capacitor Cc. A buffer amplifier drives two capacitors which do some feed forward in the voltage amplifier stage. The LMC662 does not have a classical output buffer stage.


(https://www.richis-lab.de/images/Opamp/65x03.jpg)

Dennis M. Monticelli describes the LMC662 in great detail in the IEEE article "A Quad CMOS Single-Supply Op Amp with Rail-to-Rail Output Swing". The complete circuit including the layout of the individual transistors is shown there.


(https://www.richis-lab.de/images/Opamp/65x04.jpg)

The differential amplifier at the input is classically constructed with a current source and a current mirror. The IEEE paper explains that p-channel MOSFETs without additional threshold doping were used as input transistors. This type of MOSFET would have the least noise.

The LMC662 does not provide a way to adjust the offset voltage, not even after production. Nevertheless, the values for offset voltage and drift are quite good.


(https://www.richis-lab.de/images/Opamp/65x05.jpg)

The transistors M5, M19, M20 and M6 amplify the output signal of the differential amplifier and thus drive the output stage. The IEEE paper specifies a gain factor of 40dB. Z1 limits the voltage and thus the current at the output of the LMC662.

Q23 and M22 represent the amplifier stage driving the feedforward capacitors. Cff is connected to the output of the amplifier stage seen here. Cf leads to the output stage.


(https://www.richis-lab.de/images/Opamp/65x06.jpg)

Transistor Q7 provides the driver for the M8/M9 push-pull output stage. According to the IEEE paper, the complex bias circuit ensures that the quiescent current of the output stage does not vary with supply voltage and process variations.


(https://www.richis-lab.de/images/Opamp/65x08.jpg)

(https://www.richis-lab.de/images/Opamp/65x09.jpg)

The LMC662AMJ variant, which is specified for the maximum temperature range, is shipped in a ceramic housing.


(https://www.richis-lab.de/images/Opamp/65x10.jpg)

(https://www.richis-lab.de/images/Opamp/65x11.jpg)

The edge length of the die is 1,9mm. The IEEE paper states that a 4µm process with two layers of poliysilicon is used, which was actually optimized for digital CMOS circuits. This can be very useful if you want to combine this opamp with digital circuits.


(https://www.richis-lab.de/images/Opamp/65x16.jpg)

As will become clear later, the quad opamp LMC660 and the dual opamp LMC662 basically share the same die. They differ just in the metal layer. This metal layer here shows the designation LMC662. The letter A could stand for a first revision.


(https://www.richis-lab.de/images/Opamp/65x18.jpg)

Seven mask revisions are shown in the center of the die. Accordingly, a mask has been revised once. The structures next to the mask revisions allow an evaluation of the imaging quality.


(https://www.richis-lab.de/images/Opamp/65x17.jpg)

On the right edge, seven complex structures are shown under the National Semiconductor logo. Dots number the structures. Here, in addition to the imaging performance, the alignment of the masks against each other can be checked.


(https://www.richis-lab.de/images/Opamp/65x12.jpg)

The magazine "Electronics Design Network" (11/2012) contains a picture of the LMC660 quadruple operational amplifier. According to the text, it is a representation that was used for troubleshooting. The different masks were printed with different colors on several foils. If one puts the foils on top of each other, overlapping layers create mixed colors and one can check the structures quite efficiently.


(https://www.richis-lab.de/images/Opamp/65x15.jpg)

The already referenced IEEE paper contains a picture of the structures of the LMC660. Thick black lines show the areas of the four operational amplifiers. In the left area, the bias circuit is marked.


(https://www.richis-lab.de/images/Opamp/65x13.jpg)

The input transistors M1/M2 (green) and the transistors of the associated current mirror M3/M4 (yellow) are each located in places where they are disturbed as little as possible. On the one hand, thermal gradients are problematic, which result primarily from the power dissipation of the output stage transistors (red). The alignment of output stages and input transistors on the symmetry axes ensures that thermal gradients have a very similar effect on both paths of the differential amplifier and thus compensate each other. Another issue is mechanical stress that result from integration into the package. These loads are also lowest on the symmetry axes.


(https://www.richis-lab.de/images/Opamp/65x14.jpg)

Apart from the metal layer, the dual opamp LMC662 uses the same design as the quadruple opamp LM660. The two opamps on the right and bottom edge remain unused here.


(https://www.richis-lab.de/images/Opamp/65x19.jpg)

(https://www.richis-lab.de/images/Opamp/65x20.jpg)

The individual components of the opamp can still be recognized quite well despite the two layers of polysilicon. Particularly noticeable are the three large capacitors next to the input and the output stage transistors.

The inputs of the opamps are equipped with protection circuits. According to the IEEE article, there is a 20Ω current-limiting resistor, followed by protective diodes to the supply potentials. The presence of these diodes is noteworthy because their leakage current must be low enough not to raise the very small input current of the opamp too much. In this context, it is surprising that the IEEE paper specifies a summed leakage current of 50fA, while the bias current should typically be just 2fA.  :-//


(https://www.richis-lab.de/images/Opamp/65x21.jpg)

Under the metal layer there are four complete opamps. The metal layer above the unused opamps has been heavily modified. The main reason seems to be the different pinning in the smaller package. In order to connect the pins to the circuit in a meaningful way, the bondpads had to be moved.


(https://www.richis-lab.de/images/Opamp/65x22.jpg)

The input transistors M1/M2 consist of eight circular elements each, which are interleaved in such a way that thermal gradients affect both paths of the differential amplifier as equally as possible. A similarly strong interleaving is implemented in the OPA627 (https://www.richis-lab.de/Opamp22.htm (https://www.richis-lab.de/Opamp22.htm)). The transistors M3/M4, which represent the current mirror of the differential amplifier, are each divided into at least two transistors and cross-connected.

The source contacting (red) is inconspicuous. However, the IEEE paper describes that the different distances to the individual transistors are quite critical and can lead to an unbalanced behavior of the differential amplifier. Accordingly, 50 different configurations were simulated until the structure seen here was deemed optimal.


(https://www.richis-lab.de/images/Opamp/65x23.jpg)

The highside and lowside transistors are quite large so that they can handle the high output currents.


(https://www.richis-lab.de/images/Opamp/65x07.jpg)

In a CMOS circuit, generating a stable reference voltage is a challenge. In the LMC662, one uses a bandgap reference based on the two special NPN transistors Q26/Q27. These are partially lateral bipolar transistors that can be implemented within a CMOS process.


(https://www.richis-lab.de/images/Opamp/65x25.jpg)

The structure of such a lateral bipolar transistor can be seen in the IEEE publication "Photodetection With Gate-Controlled Lateral BJTs From Standard CMOS Technology". An n-channel MOSFET inherently contains a parasitic NPN transistor, which has been subsequently colored red here. To use this transistor, the gate of the MOSFET must be connected in such a way that this area is always blocked.

The construction contains a second, parasitic collector. This must be connected to the positive supply potential so that the transistor remains isolated from the substrate. At the same time, however, this means that a current flows through this collector that is proportional to the current through the lateral collector. In order for the lateral collector to take a relevant share of the current, it must be placed as close as possible to the emitter. The current distribution is strongly influenced by production variations and cannot be controlled excessively well. The circuit of the bandgap reference ensures that this tolerance does not have an excessive influence on the reference voltage.


(https://www.richis-lab.de/images/Opamp/65x24.jpg)

(https://www.richis-lab.de/images/Opamp/65x26.jpg)

Viewed from above, such CMOS NPN transistors have a concentric structure. As usual for a bandgap reference, the two transistors Q27/Q26 have emitter areas of different sizes. In the LMC662, the ratio of the areas is 4:1.

Emitter and gate are connected to each other. Here in the picture, the difference is hardly visible due to the small structures. The purple appearing area is the gate electrode, within which the individual emitters are located. Directly around the gate electrode the lateral collector C1 is tapped. The frame around this construct is the base area, which in turn is surrounded by the collector C2. While C2 contacts the positive supply, the substrate is connected to the negative supply through the outermost frame.


https://www.richis-lab.de/Opamp62.htm (https://www.richis-lab.de/Opamp62.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Gyro on January 20, 2023, 08:46:35 pm
Well I guess that puts the bootstrapped input protection diode theory to rest then :(  They must have really low (or balanced) leakage currents.

That's a great write-up, thanks.  I'm not sure there are many opamps that switch between dual and quad with just a metalization change (?).
Title: Re: Opamps - Die pictures
Post by: RoGeorge on January 20, 2023, 08:55:15 pm
Wow, amazing work, thank you!  :o
Will take a closer look, side by side.

The IEEE article online (doi:10.1109/jssc.1986.1052645):
http://class.ece.iastate.edu/djchen/ee501/2008/MonticelliRailToRailOutSwing.pdf (http://class.ece.iastate.edu/djchen/ee501/2008/MonticelliRailToRailOutSwing.pdf)

Thanks again, I was very curious about LMC662.  :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on January 21, 2023, 11:58:06 am
It was a pleasure!  :-/O ^-^

If we believe the IEEE paper the effective leakage of the protection diodes is quite high with 50fA. Somehow that doesn't fit with the 2fA bias current.  :-//

No, you don't see it often that single/dual/quad opamps share the same die. You need more silicon but your mask set is the same (except for the metal mask). Perhaps they even build some bathes without the metal layer and when stock is low they finish the wafer depending on what configuration is needed.  :-//

I will do the LMC60x2 too. But have to heat up the furnace for these...  :-/O
Title: Re: Opamps - Die pictures
Post by: magic on January 21, 2023, 09:47:38 pm
The structure of such a lateral bipolar transistor can be seen in the IEEE publication "Photodetection With Gate-Controlled Lateral BJTs From Standard CMOS Technology".
This paper refers to some special "triple-well" CMOS process. These nested P and N wells are not normal.

LMC660 is made on ordinary P-well process, with P-ch devices fabricated directly in the N substrate and N-ch devices in P-wells embedded into the substrate. The substrate is biased to VCC. All those NPN emitter followers are described as "substrate NPNs" by Monticelli and the substrate constitutes their collectors. Collector connections visible around them must be to the substrate, or some surface N+ ring surrounding the P-well.
Title: Re: Opamps - Die pictures
Post by: David Hess on January 21, 2023, 11:25:35 pm
No, you don't see it often that single/dual/quad opamps share the same die. You need more silicon but your mask set is the same (except for the metal mask). Perhaps they even build some bathes without the metal layer and when stock is low they finish the wafer depending on what configuration is needed.  :-//

In the past the quad die would not have fit inside the dual package.  Parts like the original SO-8 LT1013 had to have the dual operational amplifier rotated 90 degrees to even fit the dual die, leading to a different pinout.
Title: Re: Opamps - Die pictures
Post by: Noopy on January 22, 2023, 04:53:56 am
The structure of such a lateral bipolar transistor can be seen in the IEEE publication "Photodetection With Gate-Controlled Lateral BJTs From Standard CMOS Technology".
This paper refers to some special "triple-well" CMOS process. These nested P and N wells are not normal.

LMC660 is made on ordinary P-well process, with P-ch devices fabricated directly in the N substrate and N-ch devices in P-wells embedded into the substrate. The substrate is biased to VCC. All those NPN emitter followers are described as "substrate NPNs" by Monticelli and the substrate constitutes their collectors. Collector connections visible around them must be to the substrate, or some surface N+ ring surrounding the P-well.


Thanks for the hint to the tripple well process! I haven´t thought about that.
But in my view that is more likely than your explanation. Are you sure about your interpretation?


(https://www.richis-lab.de/images/Opamp/65x20.jpg)

The structure of the NMOS transistors (for example in the upper left corner) would fit perfectly to a tripple well process. If the massive V- contacts a p-well here what is the inner structure that contains the four NMOS?

Monticelli talks about substrate NPNs because they basically work like this even if it just the "substrate well". "Tripple well NPN" would sound strange.  ;)

To be honest I´m not 100% sure... Will think about it the rest of the day. :phew:

What would be the V- connection I called "SUB" if C2 contacts the substrate?
Title: Re: Opamps - Die pictures
Post by: magic on January 22, 2023, 10:47:10 am
On page 1 Monticelli clearly calls it "a conventional 4-µm, double-polysilicon, P-well process optimized for digital chips".

On page 4: "[input] devices are built in the substrate" - input devices are P-ch, so the substrate is N and must be biased positive for functional junction isolation, this is shown on fig. 2.

On page 6: "These needs are all met by equipping the substrate n-p-n's with lateral collector elements" (about the bias circuit).

This bias circuit construction wouldn't make sense if nested wells were available. In such technology it could be simply realized with ordinary vertical NPNs embedded in negative-biased P substrate. But vertical NPNs with free collectors are not available in P-well process (the collector is the substrate = VCC) and hence all the gymnastics with adding lateral collectors.

Rings surrounding P-wells could be P guard rings intended to intercept minority carriers (holes) injected by the wells into the substrate during ESD events, before they are "collected" by some other P-well and trigger further disruption of circuit operation and possibly latch-up. I'm guessing here, I'm not nearly as familiar with CMOS as with classic bipolar, but I recall reading about such things.
Title: Re: Opamps - Die pictures
Post by: Noopy on January 22, 2023, 11:15:32 am
I agree with you. Thanks for the explanation!  :-+

I will change the pictures/text...
Title: Re: Opamps - Die pictures
Post by: Noopy on January 22, 2023, 11:43:38 am
(https://www.richis-lab.de/images/Opamp/65x26.jpg)

It´s no big difference but it should look like this.

It  sounds plausible that the guard ring collects free charge carriers. In the end there are a lot of charges flowing through the substrate and it is a precision circuit.

Thanks again to magic!  :-+
Title: Re: Opamps - Die pictures
Post by: exe on January 22, 2023, 08:45:24 pm
If we believe the IEEE paper the effective leakage of the protection diodes is quite high with 50fA. Somehow that doesn't fit with the 2fA bias current.  :-//

Could it be that the upper diode sources 50fA current, and lower one sinks 50fA, making it 50fA-50fA=0fA? (if they are matched)
Title: Re: Opamps - Die pictures
Post by: Noopy on January 22, 2023, 08:50:49 pm
If we believe the IEEE paper the effective leakage of the protection diodes is quite high with 50fA. Somehow that doesn't fit with the 2fA bias current.  :-//

Could it be that the upper diode sources 50fA current, and lower one sinks 50fA, making it 50fA-50fA=0fA? (if they are matched)

It doesn´t sound like that:
"The input bias and input offset currents that result from these protection diodes are dominated by the upper diodes which consistently outleak the bottom diodes causing the bias current to always exit the pins. This current is exceptionally low and typically only 50fA at room temperature (even less in plastic)."

I have no explanation for that...  :-//
Title: Re: Opamps - Die pictures
Post by: T3sl4co1l on January 22, 2023, 09:30:19 pm
In general, diode leakages won't balance; it also depends on voltage so you'd expect an open input to hover somewhere between VDD/VSS, probably a couple diode drops off one or the other rail since the leakage changes fastest (read: lowest dynamic resistance) near zero.  And the middle value (at halfway between VDD/VSS) will be +/-(Ileak minus a little bit).

Evidently the diodes here are asymmetrical, so that that balance condition never happens.  Geometry? Doping? Who knows..  They don't look very different here so it's maybe not geometry, but your eyes are better trained at this than me.

Tim
Title: Re: Opamps - Die pictures
Post by: magic on January 22, 2023, 10:26:27 pm
Current cancellation tricks can normally be detected by measuring shot noise, which adds rather than cancels, but here bias current is much too low for that. If the two currents are a few fA each and the difference between them is 2fA which becomes the externally visible Ib, then it would take several TΩ of input series resistance to easily detect noise current above Johnson noise of the resistor (if I got the math right).

The "diodes" are said to be transistors. Probably like this:
Code: [Select]
IN+ ---- P               P ---+
|    N - N -- VCC -- N - N    |
|    P - P -- GND -- P - P    |
+--- N               N ---- IN-

According to Monticelli, protection circuit is supposed to become an SCR when overvoltage appears across the two inputs with the chip out of circuit. This is what should happen here: the pins are clamped together without developing much GND-VCC voltage. I think ::)

The transistors are of different polarity so their BE junctions necessarily have different design and properties. I suppose the NPN may be a substrate NPN, while the PNP may be a lateral PNP with substrate base and two concentric P implants for emitter and collector.

Looking closely at Zeptobars LMC6001 image one can see that the two structures are slightly different; the lower one has some sort of line going through the middle of the purple ring.
Title: Re: Opamps - Die pictures
Post by: magic on January 22, 2023, 10:29:58 pm
If we believe the IEEE paper the effective leakage of the protection diodes is quite high with 50fA. Somehow that doesn't fit with the 2fA bias current.  :-//

Could it be that the upper diode sources 50fA current, and lower one sinks 50fA, making it 50fA-50fA=0fA? (if they are matched)
Probably not because the spec has been revised.

Monticelli says 50fA.
Early datasheets say 40fA.
Post 1990 datasheets say 2fA.

 :wtf: :-//
Title: Re: Opamps - Die pictures
Post by: David Hess on January 23, 2023, 12:45:17 am
Evidently the diodes here are asymmetrical, so that that balance condition never happens.  Geometry? Doping? Who knows..  They don't look very different here so it's maybe not geometry, but your eyes are better trained at this than me.

They do not use actual diodes even though they are available on the IC process.  Bipolar transistor junctions are used because they have much lower leakage and higher conductance, yielding much higher impedance at low voltages.
Title: Re: Opamps - Die pictures
Post by: Noopy on January 23, 2023, 03:55:20 am
If we believe the IEEE paper the effective leakage of the protection diodes is quite high with 50fA. Somehow that doesn't fit with the 2fA bias current.  :-//

Could it be that the upper diode sources 50fA current, and lower one sinks 50fA, making it 50fA-50fA=0fA? (if they are matched)
Probably not because the spec has been revised.

Monticelli says 50fA.
Early datasheets say 40fA.
Post 1990 datasheets say 2fA.

 :wtf: :-//

It sounds like Monticelli wasn´t able to get lower than 50fA (perhaps he wasn´t able to meassure lower currents) and later they realized they can specify 2fA (perhaps with a better process or just with better measurement equipment).

Remember the problems Bob Pease had with measuring extremly low input bias currents...
Title: Re: Opamps - Die pictures
Post by: Noopy on February 03, 2023, 08:06:11 pm
(https://www.richis-lab.de/images/Opamp/66x01.jpg)

The OP284 is a dual opamp with a rail-to-rail input and a rail-to-rail output. The supply can be selected between 3V and 36V. At 5V the OP284 draws a maximum of 1,45mA. The bias current of the bipolar input transistors is typically 60nA. The maximum offset voltage is 65µV in the best bin. The datasheet specifies the slewrate as 2,4V/µs and the bandwidth as 3,5MHz. In addition to the OP284, a device with one (OP184) and a device with four opamps (OP484) are available.


(https://www.richis-lab.de/images/Opamp/66x02.jpg)

The circuit diagram in the datasheet shows how a rail-to-rail input is usually built. To understand the circuit, it´s useful to mark the relevant blocks with different colors. There are two inverse input stages at the input. The cyan differential amplifier (R3/R4/Q3/Q4/QB3) works up to a common mode voltage equal to the positive supply voltage. If the common mode voltage drops to the negative supply, the green differential amplifier (R1/R2/Q1/Q2/QB6) takes over. QL1 and QL2 (gray) are protection structures that limit the voltage at the input.

The bias currents of opamps with rail-to-rail input stages are often discontinuous and not infrequently subject to strong component scatter. This complicates the compensation in the application. The OP284 datasheet specifies a largely linear relationship between the common-mode voltage and the bias current. However, the impression is deceptive, since a common mode voltage range of -15V to 15V is shown there. About 1V before the voltage limits, the slope of the curve changes very strongly, because one of the differential amplifiers stops working there. With a voltage range of 30V, the 1V wide marginal areas do not appear too critical. With a supply voltage of 3V, however, this characteristic is much more problematic.

The differential amplifiers are followed by a so-called compound folded cascode gain stage. In this stage, the transistors Q7/Q8 and Q5/Q6 each represent a cascode circuit. The outputs of the two differential amplifiers are combined in this section too. This is followed by the driver stage for the output (red), in which transistor Q10 works together with current sink QB7. Unusual are the four transistors Q11/Q12/Q9/Q10 (yellow), whose function is not directly obvious.  :-//

In the left area the reference current for the current mirrors is generated, which are used for biasing.

The output stage has a PNP transistor in the highside path and a NPN transistor in the lowside path, so that the output potential can be controlled almost to the supply potentials. The only limiting factor here is the saturation voltage of the output stage transistors, which is specified in the OP284 as 20mV for the lowside and 100mV for the highside. In the output stage block there is the capacitor CC2 for bandwidth limiting and the capacitor CFF, which realizes a feed forward control. At the lowside transistor the capacitor CO between base and collector reduces the tendency of oscillations.


(https://www.richis-lab.de/images/Opamp/66x03.jpg)

The chip above, which is still marked as a PMI component and dates back to 1995, was lost during the final cleaning, which is why just this non-optimal image is available.

In the lower left area, there is the abbreviation PMI and the letter sequences JRB and DSC, which could be abbreviations of the engineers. In the lower right corner, you can already see the logo of Analog Devices. Analog Devices bought PMI in 1990. Below that, the year 1994 was recorded. At the upper edge, a typical PMI designation is found with the string 1446Z. Z stands for the first revision.


(https://www.richis-lab.de/images/Opamp/66x04.jpg)

The revision 0 of the datasheet shows the metal layer of the OP284. According to this, the dimensions are 2,34mm x 1,65mm and contains 62 transistors. If you would double the schematic above, you would get 64 transistors. This indicates that the two integrated opamps share the reference current generator.


(https://www.richis-lab.de/images/Opamp/66x05.jpg)

The metal layer of the OP484 with four opamps is shown in the datasheet too. This variant apparently was designed one year later. The die is 2,79mm x 2,03mm and contains 120 transistors. The designation is 1447Z.


(https://www.richis-lab.de/images/Opamp/67x01.jpg)

This OP284 dates from 1997 and already shows the Analog Devices logo.


(https://www.richis-lab.de/images/Opamp/67x02.jpg)

The die is protected with a gel potting, which was used in the upper OP284 too.


(https://www.richis-lab.de/images/Opamp/67x03.jpg)

It turns out that this OP284 already contains revision Y, i.e. the second revision of the opamp. There are no obvious functional differences to the first revision. Most noticeable are slightly different spacing of the metal layer at the large capacitors. Perhaps the mask set just needed to be adapted to new production lines.

The die is very symmetrical, but not completely symmetrical. The two opamps are mirrored on the vertical axis, but the inputs are on the lower left and upper right to represent the usual pinning for a dual opamp. It is interesting to note that the resistors located directly at the inputs are present at the bottom for both opamps. Likewise, two input resistors have been integrated just above the center of the die twice. I assume that this is not just a reservation to place the two inputs at the lower edge. Apparently one wanted to keep the structures under the metal layer maximally symmetrical.

The die was laser tuned. This can be seen in the typical resistor geometries and the square test structure at the top left. The resistor pairs with the bulges are used to match the offset of the doubled input amplifiers. In the center, where the reference of the biasing circuits is located, a small network of resistors is integrated, which can be used for tuning too.

The input transistors and the protection diodes are located in the center of the die. The output stages are integrated on the horizontal axis at the edges, so that their heat dissipation affects the branches of the differential amplifiers as evenly as possible and does not create thermal drift effects.

It turns out that the capacitors have a somewhat more complex structure than shown in the schematic. In the large capacitor block, whose lower electrode is connected to the output, in addition to the two known capacitors CO and CC2 there is a not connected spare capacitor. Another capacitor represents an additional capacitor connected to the emitter of transistor Q15. This measure inhibits oscillation of the highside transistor. The capacitor CFF, which is used for feed forward, is located in the upper area of the die and consists of two surfaces. The second surface is connected to the emitter of transistor Q15 and acts as a feed forward path too.


https://www.richis-lab.de/Opamp63.htm (https://www.richis-lab.de/Opamp63.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on February 04, 2023, 10:50:32 am
Unusual are the four transistors Q11/Q12/Q9/Q10 (yellow), whose function is not directly obvious.  :-//
Same story as OP283.

Q9 is a driver for Q5,Q6 and Q10 drives Q18.

Q11,Q12 may initially look pointless, but I think they are there for base current compensation. If Q10 base current increases due to base current of Q18, Q11 base current increases (almost) the same. Then Q5,Q6 current decreases the same and thus Q8 provides the necessary base current into Q10, without the input stage needing to do (almost) anything. This should increase open loop gain under heavy loading and reduce input offset voltage (and drift) due to mismatch in Q9,Q10 quiescent currents. Q12 works the same way for Q9.
Title: Re: Opamps - Die pictures
Post by: magic on February 04, 2023, 03:31:01 pm
No one noticed that these are vertical PNPs, fabricated in isolation islands biased to VCC.
Looks like OP283 was made the same way, but I didn't see it then.
 :popcorn:

Not sure how they managed to break the usual (for bipolar) 3:1 ratio between bandwidth in MHz and slew rate in V/μs.
Unlike OP283, this one doesn't have emitter degeneration. (Now you know why I noticed those weird PNPs).
Title: Re: Opamps - Die pictures
Post by: Kleinstein on February 04, 2023, 07:08:53 pm
The open loop gain and phase curves look a bit unusual. There are different values for the GBW product depending on which frequency range to look at. When looking at the low freuquency end one gets a considerably larger GBW product and thus about the usual ratio.  The 2 (NPN and PNP)  input stages and how the compensation is done seems to be causing this somewhat inusual reponse.
Title: Re: Opamps - Die pictures
Post by: Noopy on February 04, 2023, 08:14:23 pm
Unusual are the four transistors Q11/Q12/Q9/Q10 (yellow), whose function is not directly obvious.  :-//
Same story as OP283.

Q9 is a driver for Q5,Q6 and Q10 drives Q18.

Q11,Q12 may initially look pointless, but I think they are there for base current compensation. If Q10 base current increases due to base current of Q18, Q11 base current increases (almost) the same. Then Q5,Q6 current decreases the same and thus Q8 provides the necessary base current into Q10, without the input stage needing to do (almost) anything. This should increase open loop gain under heavy loading and reduce input offset voltage (and drift) due to mismatch in Q9,Q10 quiescent currents. Q12 works the same way for Q9.

Indeed, we had the same questions with the OP283, quite a long time ago...  ::)
In the OP284 it´s even a little more puzzling but your explanations back then and today sound reasonable.


Regarding GBW and slewrate: These feedforward and compensation capacitors possible do some strange things to the behaviour at different frequencies.  :scared:
Title: Re: Opamps - Die pictures
Post by: Noopy on February 05, 2023, 04:47:09 pm
(https://www.richis-lab.de/images/Opamp/68x03.jpg)

(https://www.richis-lab.de/images/Opamp/68x01.jpg)

This is an easy one: Siemens TAA521, another 709 variant.


(https://www.richis-lab.de/images/Opamp/68x02.jpg)

(https://www.richis-lab.de/images/Opamp/68x05.jpg)

(https://www.richis-lab.de/images/Opamp/68x04.jpg)

It can be seen that the design of the die is almost exactly the same as in the National Semiconductor LM709 from 1969 (https://www.richis-lab.de/Opamp54.htm (https://www.richis-lab.de/Opamp54.htm)). The metal layer shows just small, non-functional differences in some places. On the left side you can find the characters 709F as in the LM709 from National Semiconductor.


https://www.richis-lab.de/Opamp64.htm (https://www.richis-lab.de/Opamp64.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on February 10, 2023, 09:11:59 pm
Finally I managed to update the AMP01. It was one of my first projects and first I had just "normal" pictures just showing the metal layer. I wrote A LOT of words around the pictures but that didn´t compensate the lack of information. Since the AMP01 is a really nice part it deserves better pictures and explanations:


(https://www.richis-lab.de/images/amp01/03_01.JPG)

(https://www.richis-lab.de/images/amp01/03_02.JPG)

The AMP01 is an instrumentation amplifier developed by Precision Monolithics, which still costs over 30€ today and is now distributed by Analog Devices.

The datasheet specifies a maximum offset voltage of 50µV. The temperature drift is a maximum of 0,3µV/°C. The bias current remains below 4nA. The amplification factor can be selected between 0,1 and 10.000. With a gain factor of 1.000, the linearity is sufficient for an accuracy of 16Bit. The datasheet specifies a common mode rejection of at least 125dB. An output level of up to +/-10V is regulated with up to +/-50mA. A maximum of +/-13V is possible. Capacitive loads of up to 1µF are also permissible. For a gain factor of 1.000, the datasheet specifies a -3dB bandwidth of typically 26kHz. The slew rate is 4,5V/µs (G=10). The settling time is 50µs (G=1000, 20V, +/-0,01%).


(https://www.richis-lab.de/images/amp01/03_03.jpg)

The datasheet of the AMP01 contains a block diagram that shows how the amplifier works. In the centre there are two balanced amplifier branches that process the input signals. The amplification factor of this differential amplifier and thus of the entire component can be adjusted via the resistance between the branches. This is called "cross degeneration" or "pi degeneration".

The two branches are supplied by two current sources. Two current sinks are located at the lower ends of the differential amplifier branches. Both pairs of current sources can be adjusted independently of each other, thus enabling the offset voltages at the input and output of the AMP01 to be balanced. According to the datasheet, the current ratio above the input transistors can be used to compensate for the offset voltage at the input, which is then multiplied by the amplification factor. It is noticeable that the circuit diagram just represents reality in a very simplified way. Here, the upper current sources would just influence the offset voltage at the output. The set amplification factor would have no influence.

With the current ratio below the input transistors, one can compensate the offset voltage at the output. A different current ratio leads to a current flow across the resistor Rs, which in its main function defines the strength of the sense feedback. This also makes it possible to adjust the offset voltage at the output.

For gain factors above 50, the datasheet recommends adjusting the offset voltage at the input. For amplification factors below 50, however, the offset voltage at the output should be adjusted, as this is initially higher if the amplification factor is left out. If you want to adjust both offset sources, start with a short-circuited resistor Rg at the input offset, then remove the short-circuit and adjust the output offset.

Below the input transistors there are two additional transistors that influence the signals in the branches. On the right side is the sense potential, which is connected directly to the output or, in the case of four-wire connection, to the actual destination point of the output signal. Since the AMP01 can drive relatively high currents, such feedback of the output signal is quite useful. The transistor in the left path is controlled by the reference pin. This potential can be connected directly to the local ground or, with four-wire connection, to the reference potential at the destination point.

The levels of the sense and reference potentials are adjusted via voltage dividers that are integrated on the chip. This means that no particularly constant resistors are required externally. There is usually hardly any voltage at the reference input, but an identical voltage divider has been integrated on this side as well. This design ensures the best possible symmetry. Temperature drifts have the same effect on both sides and compensate each other. This is another advantage of integration on the chip. Both voltage dividers thus have very similar temperatures. The operational amplifiers between the voltage dividers and the differential amplifier branches ensure that the high-impedance voltage dividers are not loaded.

A resistor is to be connected to the contacts Rs, which acts as an emitter resistor like Rg, but is assigned to the transistors above it in the feedback paths. Like Rg, Rs represents a local negative feedback. However, since the local negative feedback at Rs relates to the global negative feedback, Rg and Rs have an inverse effect. A low resistance Rg results in a high amplification factor. A low resistance Rs provides a low amplification factor. The opposite influence on the amplification has the positive side effect that thermal drifts of the resistors at least partially compensate each other.

There is a buffer amplifier at the output of the differential amplifier. On the one hand, this prevents the load at the output of the differential amplifier from having a negative effect on its specifications. On the other hand, the buffer amplifier also makes it possible to connect higher loads to the instrumentation amplifier. This can be a 50Ohm system, but it can also just be a longer transmission line with a large parasitic capacitance.


(https://www.richis-lab.de/images/amp01/03_04.jpg)

The datasheet shows the metallisation layer of the instrumentation amplifier. The dimensions of the die are therefore 2,82mm × 3,78mm.


(https://www.richis-lab.de/images/amp01/03_05.jpg)

The present die corresponds pretty much exactly to the representation in the datasheet.


(https://www.richis-lab.de/images/amp01/03_07.JPG)

1411 is the internal designation of the circuit. The W indicates the revision. In the case of PMI, this was done by counting up from Z in the direction of A. This is therefore the fourth revision.

The character string 6A1 stands for the mask of the metal layer. On the right edge of the dies are the abbreviations of eight other masks.


(https://www.richis-lab.de/images/amp01/03_08.jpg)

(https://www.richis-lab.de/images/amp01/03_09.jpg)

The design dates back to 1987. GBW and DFB are probably abbreviations of the developers involved. Two patents mentioned in the datasheet belong to Derek F. Bowers.


(https://www.richis-lab.de/images/amp01/03_06.jpg)

On the upper edge, the masks depict eight small squares. Next to them is an integrated symbol that cannot be assigned.


(https://www.richis-lab.de/images/amp01/03_16.jpg)

At first glance, the layout of the die appears confusing, but the critical circuit parts are arranged very advantageously. The majority of the critical elements are integrated symmetrically around the horizontal axis in the center of the device. If the output stage on the far right heats up, the differential paths experience a similar temperature change and drift defects compensate to a large extent.


(https://www.richis-lab.de/images/amp01/03_10.jpg)

The AMP01 offers two supply interfaces. One interface supplies only the output stage (yellow/green). The other interface supplies the remaining circuit parts (red/blue).


(https://www.richis-lab.de/images/amp01/03_15.jpg)

The input transistors are positioned with their input resistors on the far left (white). The protection diodes are positioned a little to the top. The feedback control transistors (blue) connect the input transistors to the current sinks (pink). The current sinks themselves are in the middle of the die. At the lower edge, an adjustment takes place during production. In addition, the potentials that enable an external adjustment intervene here.

The current sources that supply the input transistors are located between the input transistors and the current sinks (red). Again, there are circuit parts for an adjustment during production and the intervention for an adjustment in the later application. Both are located in the upper left corner of the die. However, it is not the current source that is influenced there, but more or less current sinks connected in parallel.

The input transistors are protected from voltage fluctuations at the collector by a cascode circuit (orange). This part of the circuit is not shown in the datasheet. It is located between the input transistors (white) and the current sources (red).

The coupling of the signals to the output amplifier (cyan) is done from the circuit part that do the input current compensation. The input current compensation is located in the lower left corner and takes up quite a large area (black). The circuit feeds the necessary base currents into the inputs of the instrumentation amplifier. The compensation circuit works with two current sources placed further to the right, one of which can be adjusted via a test pad. According to the circuitry, the strength of the compensation can be adjusted here.


(https://www.richis-lab.de/images/amp01/03_30.jpg)

If we record the circuit of the large differential amplifier, we get the circuit diagram shown here. There are many more current sources and sinks in the circuit than shown in the datasheet. They do biasing in many places.

As expected, the offset voltage at the input is not adjusted directly at the current sources ViosNULL. The two current sinks ViosNULL are located above the input transistors and the two current sinks IQ1/IQ2 are integrated below. To adjust the offset, the current ratio of these pairs is changed. Changes have an inverse effect on ViosNULL and IQ1/IQ2. Ultimately, the input offset is influenced via the current sinks IQ1/IQ2, whose differential current flows through the resistor Rg. The current sinks ViosNULL ensure that the current ratio in the upper area isnot excessively influenced.


(https://www.richis-lab.de/images/amp01/03_32.jpg)

The design and characteristics of the input amplifier are described in more detail in patent US4471321. This patent is mentioned in the datasheet of the AMP01. The circuit fulfils two important tasks in addition to the basic function of a differential amplifier. It ensures that the potentials at the input transistors change as little as possible and that the external circuitry is loaded as little as possible by the input currents.

The cascode circuit in the immediate vicinity of the input transistors fixes their collector-emitter voltage and thus ensures strong common-mode rejection (I4/Q8/Q7/Q9 and I5/Q11/Q10/Q12).

In the right-hand section, the input circuit is shown a second time. In the centre are two SuperBeta transistors (Q14/Q15), as they are also used at the inputs of the AMP01 (Q1/Q2). In this connection, they draw a base current that corresponds to the base current of the input transistors. It does not have to be the absolute same current value, but the ratio of the currents has to be the same. Necessary amplification factors can be set by the following current mirrors. The bias cancellation thus ensures that a current is fed into the inputs of the AMP01 that corresponds fairly exactly to the base current of the input transistors. This ensures that the circuit at the inputs of the AMP01 is not loaded with the base currents.


(https://www.richis-lab.de/images/amp01/03_11.jpg)

The two input transistors Q1 and Q2 are each divided into two areas arranged crosswise so that temperature gradients affect both branches of the differential amplifier as equally as possible.

The external resistor Rg, which also determines the amplification factor, is connected with two bondwires. Since Rg may have quite a small value, special care must be taken to ensure that the influence of the connection lines and thus also of the bondwires remain as small as possible.


[...]

Title: Re: Opamps - Die pictures
Post by: Noopy on February 10, 2023, 09:12:57 pm
(https://www.richis-lab.de/images/amp01/03_29.jpg)

The transistors of the two large current sources and the two large current sinks are also doubled and cross-connected. In addition, the two circuit parts are located on the horizontal symmetry axis of the die. This guarantees that thermal gradients also affect the two branches of the differential amplifier as evenly as possible.

The lines leading from the emitter resistors of the current sinks to the ground potential contain meanders, so that they also represent as equal resistances as possible. A closer look reveals that equal lengths were also taken into account for the supply lines of the current sources.


(https://www.richis-lab.de/images/amp01/03_20.jpg)

To adjust the current sinks of the large differential amplifier, there are additional emitter resistors connected in parallel at the lower edge of the die. These can be connected via fuses and thus enable the current sinks to be adjusted during production. One branch offers four fuses for this purpose, the other one offers one. The user has access to these emitter resistors via the Voos NULL contacts and can further adjust the remaining offset in his circuit.


(https://www.richis-lab.de/images/amp01/03_17.jpg)

In the upper left corner of the die are some smaller current sinks which, in addition to the biasing, are used to adjust the offset voltage at the input. Like the large current sinks, the current sinks for offset adjustment can be adjusted during production via fuses and later offer the user an adjustment option via the ViosNULL contacts. Here, one path contains three fuses and the other one contains one fuse.


(https://www.richis-lab.de/images/amp01/03_31.jpg)

The Darlington transistors in the cascode circuit have a very large collector area. On the right, it serves as the supply line for the current sources and on the left, the signal is coupled out for bias cancellation and to the output opamp A1.


(https://www.richis-lab.de/images/amp01/03_14.jpg)

In the lower left corner of the die there is the bias cancellation circuit. You can clearly see the two large transistors that are similar on the input transistors, which are supposed to reproduce the electrical conditions at the inputs as well as possible.


(https://www.richis-lab.de/images/amp01/03_18.jpg)

Smaller current sources are integrated below the large current sources and current sinks. They supply the cascode circuit, the bias cancellation and the input stages of the operational amplifiers A2 and A3.


(https://www.richis-lab.de/images/amp01/03_33.jpg)

The datasheet of the AMP01 refers, among other things, to patent US4503381, from which the above circuit diagram is taken. It shows a large current mirror with two outlets. Also drawn are the leakage currents IL, which can be relatively high with the usual lateral PNP transistors. Especially when the current mirrors are to deliver small currents, these are strongly distorted by the leakage currents.

The upper transistor row (Q3/Q2/Q1) represents the actual current mirror for the reference current of transistor Q7. Transistor Q8 carries the base currents of Q1/Q2/Q3, so that these do not reduce the reference current. The lower transistor row (Q6/Q5/Q4) shields the current mirror from potential fluctuations, which increases the internal resistances of the current sources.

As a new feature, the patent describes the transistors Q10/Q11, which are designed to compensate for leakage currents in the current mirror. Since the base currents of transistors Q10 and Q11 are represented by their respective leakage currents, the collector currents contain a temperature drift that is proportional to these leakage currents. This ensures that the currents fed into the current mirror correspond to some extent to the leakage currents there.


(https://www.richis-lab.de/images/amp01/03_24.jpg)

The current mirror in the AMP01 contains the cascode transistors described in the patent above, but the leakage current compensation has not been implemented. The resistors allow different currents to be set for the individual branches.

The reference current, on which the currents of the current sources are based, is generated with a bandgap reference (not in the picture). It is interesting to note that the first current source (Q3/Q4) feeds into the reference path. Apparently, the operating current of the bandgap reference is generated here too.


(https://www.richis-lab.de/images/amp01/03_21.jpg)

In the case of the operational amplifiers A2 and A3, an attempt was made to arrange the sensitive circuit parts in such a way that thermal gradients on the die have as little effect as possible on the signals.

The voltage dividers are located in the immediate vicinity of the power amp transistors, but they are arranged axisymmetrically around the horizontal axis. Since the circuit is electrically symmetrical too, drift effects are largely compensated.

The input transistors of the operational amplifiers A2 and A3 are located next to the voltage dividers. Here the geometric and electrical symmetry ensure low thermal drift too.

Current sources, current sinks and the middle amplifier stage have to do their job with less optimal positions from the point of view of possible temperature drifts. The output stage transistors of the operational amplifiers A2 and A3 are then again optimally symmetrically placed at the corners of the input transistors.


(https://www.richis-lab.de/images/amp01/03_26.jpg)

The resistance ratio of 1:19 can be clearly seen in the voltage dividers. The lowest resistor consists of two elements, one of which is bridged. It seems that there is a possibility to adjust the resistance ratio to 2:19.

Dummy structures are integrated above and below the voltage dividers (green). These structures usually ensure that the manufacturing process affects the outer and inner resistors as equally as possible. The area in which the resistors are embedded is massively connected to the potential V+ (blue). This contact is not exclusive, as it also supplies the output stage next to it.

Between the common base of the two voltage dividers and the potential V- is a large diode, which is not shown in the circuit diagram (cyan). The purpose of this diode remains unclear. Perhaps the temperature drift of the forward voltage should compensate another temperature drift.

To the left of the resistors, the input transistors of the operational amplifiers A2 and A3 are integrated (white). The four transistors are connected crosswise in parallel as usual. Although they are functionally just two transistors, they are the input transistors for both differential amplifiers. Each transistor has a current source in the collector path under which the output signal is tapped. The feedback from the large differential amplifier is connected to the base. The voltage dividers, via which the sense and reference potentials are supplied, are located at the emitter.


(https://www.richis-lab.de/images/amp01/03_22.jpg)

The individual circuit parts of the operational amplifier A1 are distributed over the surface of the die. The large output stage is located on the right edge of the die.


(https://www.richis-lab.de/images/amp01/03_12.jpg)

The large NPN transistors of the output stage are clearly visible. Also clearly visible are the current limiters. Among the remaining components in this area must be the overtemperature protection too.


(https://www.richis-lab.de/images/amp01/03_23.jpg)

The many current sources and sinks take up a considerable area on the die. In addition, there is a large reference voltage source in the upper right corner (yellow) and a special test circuit in the lower right corner (green).


(https://www.richis-lab.de/images/amp01/03_13.jpg)

In the area where the reference voltage or the reference current is generated, the transistor constellation typical for a bandgap reference is particularly noticeable (yellow arrows). One transistor is surrounded by a second transistor divided into two blocks. The outer transistor has an emitter area four times as large. The emitter paths contain the typical resistor constellation.


(https://www.richis-lab.de/images/amp01/03_25.jpg)

(https://www.richis-lab.de/images/amp01/03_27.jpg)

In the lower right corner there is a test circuit that has been given a surprising amount of space. It is connected to the test pin of the AMP01.

On the far left of the picture, four transistors generate four currents that are proportional to the currents of the large current source and current sink pairs. These currents are duplicated in four current mirrors and fed to a circuit with four large Darlington transistors.


(https://www.richis-lab.de/images/amp01/03_28.jpg)

Normally, the test pin is not connected, which means that the collectors of the Darlington transistors are open. In this state, just the current of the upstream current mirrors flows through the circuit. The Darlington circuit suggests that this current is very low, probably hardly relevant. Consequently, the circuit only becomes active when a supply voltage is applied to the test pin.

Surprisingly, the outputs of the four Darlington transistors feed into the lowest ranges of the resistors, which belong to the lower current sinks of the large differential amplifier. Consequently, the test circuit can actively influence the current sinks. Even more surprising is the linking of the signals. The potential of the left current sink influences the left current sink. The right current sink, however, is not only influenced by the right current sink, but also by the two upper current sources of the large differential amplifier.

Also surprising are the different values of the emitter resistors. The ratio 2:4:8:1 can be easily estimated from the geometries. The Z-diodes in parallel with these resistors limit the current flow to the emitter resistors of the lower large current sinks above a certain level. The different resistance values provide for different current limits.

Everything indicates that this test circuit is used to adjust the current sources and current sinks or to check the grade of the adjustment at the end of production. Since the test potential is applied to a pin, it can be assumed that the circuit is designed to be activated again after integration into the housing. The exact mode of operation remains unclear.


https://www.richis-lab.de/IC_05.htm (https://www.richis-lab.de/IC_05.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on February 14, 2023, 11:14:08 am
(https://www.richis-lab.de/images/Opamp/69x01.jpg)

The AMD AM685 is a fast comparator that switches with a delay of just 6,5ns. With a latch input you can fix the current state, which is advantageous when used in ADCs. In the Soviet Union the AM685 was reproduced as КP597CA1. You can find the КP597CA1 here: https://www.richis-lab.de/Opamp25.htm (https://www.richis-lab.de/Opamp25.htm)


(https://www.richis-lab.de/images/Opamp/69x03.jpg)

The datasheet contains a detailed circuit diagram.


(https://www.richis-lab.de/images/Opamp/69x02.jpg)

(https://www.richis-lab.de/images/Opamp/69x04.jpg)

(https://www.richis-lab.de/images/Opamp/69x05.jpg)

The dimensions of the die are 1,3mm x 0,8mm. The AMD logo is depicted on the lower edge. The arrangement of the individual elements has been carefully thought out. You can find more details on the site of the КP597CA1.


(https://www.richis-lab.de/images/opamp/26x04.jpg)

The КP597CA1 is clearly modeled after the AM685. The die of the КP597CA1 is just a little bigger because the bondpads have been moved further out and some test structures have been integrated in the outer area.


https://www.richis-lab.de/Opamp65.htm (https://www.richis-lab.de/Opamp65.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: iMo on February 14, 2023, 03:57:03 pm
@Noopy: I've been waiting on your book "The World of Chips in Colors", hopefully it will come out soon..  :D
Title: Re: Opamps - Die pictures
Post by: Noopy on February 14, 2023, 05:22:27 pm
@Noopy: I've been waiting on your book "The World of Chips in Colors", hopefully it will come out soon..  :D

Sounds very good!  :-+ 8)
Title: Re: Opamps - Die pictures
Post by: T3sl4co1l on February 14, 2023, 08:40:54 pm
Huh, Q5/Q6 for positive feedback?  Not rated for any hysteresis though... I wonder if Q17/Q18 emitter impedance is simply low enough not to do it (enhancing loop gain without causing hysteresis)?  They're certainly biased strongly, Q12 (Q9/Q10 in turn, depending on latch) dominates over Q11 (input diff bias).  Which makes sense for the twist-connected Q7/Q8, but I'm not sure about Q5/Q6.

D5-D8 seem to be mislabeled zeners; or maybe schottky in the process give equivalently useful breakdown voltage?

Tim
Title: Re: Opamps - Die pictures
Post by: Noopy on February 14, 2023, 08:52:30 pm
Yeah that positive feedback looks strange. Well it´s no opamp.  ;D

I would say D5-D8 are normal zener symbols. OK, not the less angular type but I know the "90° zener" too.
Title: Re: Opamps - Die pictures
Post by: T3sl4co1l on February 14, 2023, 10:57:59 pm
Hmm, they probably are different, huh.  But that's a very poorly printable distinction; in fact D4 has suffered such a printing (or scanning) error.

Curious to use such awful symbols ;) when they've done the one thing, avoid 4-way junctions. :D

Tim
Title: Re: Opamps - Die pictures
Post by: edavid on February 14, 2023, 11:49:28 pm
The design dates back to 1987. GBW and DFB are probably abbreviations of the developers involved. Two patents mentioned in the datasheet belong to Derek F. Bowers.

GBW is the late Garth Wilson, one of the founders of PMI.  Oddly enough he left PMI and went on to work on EPROMs at AMD and microprocessors at Intel.  I worked with him briefly at Intel, but to my disappointment I was never able to get him talking about his PMI (or Fairchild) days.
Title: Re: Opamps - Die pictures
Post by: Noopy on February 15, 2023, 04:07:01 am
Hmm, they probably are different, huh.  But that's a very poorly printable distinction; in fact D4 has suffered such a printing (or scanning) error.

Curious to use such awful symbols ;) when they've done the one thing, avoid 4-way junctions. :D

Tim

D4? No, i think that one is ok, it´s a Schottky.  :-//


GBW is the late Garth Wilson, one of the founders of PMI.  Oddly enough he left PMI and went on to work on EPROMs at AMD and microprocessors at Intel.  I worked with him briefly at Intel, but to my disappointment I was never able to get him talking about his PMI (or Fairchild) days.

Thank you for this information. Very interesting!  :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on February 15, 2023, 07:41:47 pm
(https://www.richis-lab.de/images/Opamp/69x06.jpg)

Hey there are the diodes D1/D2 in the transistors Q3/Q4 but they are not connected! Interesting...


https://www.richis-lab.de/Opamp65.htm#D1D2 (https://www.richis-lab.de/Opamp65.htm#D1D2)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on February 17, 2023, 08:05:05 pm
(https://www.richis-lab.de/images/Opamp/01x01.jpg)

(https://www.richis-lab.de/images/Opamp/01x02.jpg)

(https://www.richis-lab.de/images/Opamp/01x03.jpg)

Do you remember the NE5534? Some of my first pictures, so the quality is... Well...  ;D

https://www.richis-lab.de/Opamp01.htm (https://www.richis-lab.de/Opamp01.htm)




(https://www.richis-lab.de/images/Opamp/70x01.jpg)

The NE5532 is a dual opamp based on the NE5534. However, they are not exactly the same opamps. The NE5534 needs an external compensation capacitor if you want to use it with a gain smaller than 3. The NE5532, on the other hand, is already fully compensated internally. However, this also reduces the slewrate from 13V/µs to 9V/µs. The small signal bandwidth is specified as 10MHz for both variants, but the power bandwidth decreases from 200kHz to 140kHz. The DC voltage gain is reduced from 100V/mV to 50V/mV, that shows that not only the internal capacitance have been increased in the NE5534, but also the gain factor has been reduced.


(https://www.richis-lab.de/images/Opamp/70x03.jpg)

The datasheet of the NE5532 contains a detailed circuit diagram, which has been provided here with designators and colored for a better understanding. The input stage is represented by a common differential amplifier (yellow). The capacitor C1 limits the frequency band. There are two diodes at the inputs to protect against high voltages. In contrast to the NE5534, the NE5532 offers no possibility to externally adjust the offset voltage.

The current sink T3 is part of a bias network (blue). The core is a so-called "self-biased current reference" with transistors T4-T7. The transistors T6 and T7 have different sizes. Thus, as in a bandgap reference, a voltage with a small, positive temperature coefficient can be obtained at resistor R6. The resistor itself also has a positive temperature coefficient, so that the temperature coefficients largely compensate each other in the generated current. The reference voltage source is supplied by the current mirror T4/T5. The reference current is mirrored back into the reference circuit and is used as power supply. This ensures that Vcc fluctuations do not affect the reference current. The circuit R7/R8/D3 ensures a clean start-up.

The input amplifier is followed by another differential amplifier stage (green). Here no voltage amplification takes place yet. The transistors T8 and T9 work against the current mirror T11/T12. T10 ensures that the left path is not loaded with the base currents of the current mirror. A second emitter additionally feeds a current into the right path, which compensates there the base current of the following amplifier stage. Capacitor C2 allows a current to flow from the yellow amplifier stage into the right path of the green amplifier during rapid signal changes, thus providing feedforward. C3 and C4 form compensation capacitors which limit the frequency response of the opamp.

The green amplifier stage is followed by a driver stage (pink) before the transistors T17 and T19 represent the final stage (red). Only in this amplifier stage the voltage amplification of the NE5532 takes place (so that is not unique for the LMC662). A defined voltage drops at block D4/R15/T15 (gray), which provides a certain quiescent current in the output stage. The output stage has an overcurrent protection (cyan), which directly diverts the base current of the highside transistor. If an overcurrent occurs in the lowside transistor, the control of the driver transistor T13 is withdrawn via the current mirror T18/T22.

The transistor T16 seems to prevent saturation effects. If the voltage at the collector of T17 drops too far, T16 becomes conductive and consequently reduces the modulation of T13 and thus also of T17.


(https://www.richis-lab.de/images/Opamp/70x02.jpg)

The die is located relatively far off-center in the package.

On the die the two opamps are completely isolated from each other except for the substrate. Accordingly, two bondwires lead from each supply pin to the die.


(https://www.richis-lab.de/images/Opamp/70x04.jpg)

(https://www.richis-lab.de/images/Opamp/70x05.jpg)

The dimensions of the die are 3,0mm x 2,2mm. The division into two parts without an electrical connection is clearly visible. A relatively large area is taken up by the large capacitors.


(https://www.richis-lab.de/images/Opamp/70x06.jpg)

The development of the NE5534 and its variants can be traced back to Signetics. Signetics was acquired by Philips in 1975. It is therefore not surprising that there is a Signetics design in this device. This can be seen in the auxiliary structures for monitoring the manufacturing process, which can be found in the same form in other Signetics circuits, such as the NE5534 or the NE555 (https://www.richis-lab.de/555_6.htm (https://www.richis-lab.de/555_6.htm)). The string 6663A is a typical Signetics internal project designation too.

The illustration of the revisions of the seven masks shows that the metal layer was revised once.


(https://www.richis-lab.de/images/Opamp/70x07.jpg)

The integrated circuit largely corresponds to the schematic in the datasheet.

For each opamp there are three free bondpads. These are the contacts which allow an adjustment of the offset voltage and an increase of the compensation capacitor of the NE5534 and the NE5533. Most likely, the same design with an adapted metal layer is used there.


(https://www.richis-lab.de/images/Opamp/70x08.jpg)

On top of the resistors R1/R2 there is a metal surface which can be seen in NE5534 too. The metal surface is connected to the positive supply. It appears that the parasitic capacitance is used here.

The resistors R1/R2 and R9/10 provide a tuning option on one side. By moving the contacts to the metal layer one can adjust the offset voltage of the first two amplifier stages.

In the upper part of the first differential amplifier there is a significant difference to the schematic. Between the collector resistors R1/R2 and the positive supply two series connected diodes are integrated (DR). The purpose of these diodes remains unclear. These diodes are not integrated in the NE5534.


(https://www.richis-lab.de/images/Opamp/70x09.jpg)

The resistor R8 in the start-up circuit is a JFET according to the structures. The NE5532 datasheet from Texas Instruments contains a circuit diagram that is almost completely similar to the circuit diagram from Signetics. However, a JFET is actually drawn in place of the resistor R8.

The circuit R15/D4/T15, which realizes the quiescent current setting of the output stage, shows an interesting structure. The emitter area of the transistor T15 and the diode D4 are conspicuously large.

Also interesting is the transistor T3. With its three emitter areas it is ensured that the current density is similar to the current density in the reference transistor T6, which ensures a very similar behavior and thus a constant current flow through the input amplifier.


(https://www.richis-lab.de/images/Opamp/70x11.jpg)

The emitter resistors R3 and R6 of the current sinks T3 and T6 are integrated directly next to each other. The resistor R3 is designed somewhat larger with a series connection. The current mirror T4/T5 is located with the output stage on the horizontal axis of the die. Temperature gradients caused by the output stage thus have a very similar effect on the two transistors.


(https://www.richis-lab.de/images/Opamp/70x10.jpg)

The Philips and Signetics datasheets do not specify the capacities of the NE5532 in detail. The Texas Instruments NE5532 datasheet contains capacity values too. It can be assumed that the capacitances at Signetics are at least similar. Accordingly, the values are 100pF, 40pF, 12pF and 7pF. The value of C3 was obviously adjusted via the metal layer.

It is interesting that the 100pF capacitor C1 is just minimally larger than the 40pF capacitor C2. This is due to the fact that capacitor C2 consists of two electrodes. In capacitor C1, the base surface forms one electrode (red), while above it the metal layer with the emitter surface and below it the collector surface form the other electrode. The metal layer and the collector surface are connected both at the upper edge (cyan) and twice in the middle of the surface (blue). This results in a much larger capacitance per unit area, although this is voltage dependent.


https://www.richis-lab.de/Opamp66.htm (https://www.richis-lab.de/Opamp66.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on February 17, 2023, 09:33:51 pm
I will have to compare this against two Signetics branded NE5532 that I ought to have somewhere. IIRC they looked the same.
Later Philips made a different version which can be seen at Zeptobars. The new die was smaller and didn't have offset/comp pads.

Old NE5532 wouldn't fit into SO8 so the SMD version was wide SO16. Sadly, they didn't bond offset/comp to the extra pins.

Those numbers like "6663A" were different on my two dice but I couldn't see any other difference. I'm not sure if they are die versions or maybe location of the die on the wafer.

The transistor T16 seems to prevent saturation effects. If the voltage at the collector of T17 drops too far, T16 becomes conductive and consequently reduces the modulation of T13 and thus also of T17.
That's also the role of the second emitter of T10 - preventing saturation of T12. In normal operation its Vbe is zero.

In the upper part of the first differential amplifier there is a significant difference to the schematic. Between the collector resistors R1/R2 and the positive supply two series connected diodes are integrated (DR). The purpose of these diodes remains unclear. These diodes are not integrated in the NE5534.
As far as I understand, NE5532 reduces its gain by running the input stage at lower current than NE5534. This allows unity gain stability without increasing compensation caps and die area. Other consequences are lower bias current and worse voltage noise.

These diodes provide additional voltage drop to establish proper bias of the second stage, whose operating current depends on common mode voltage at T8,T9 bases.

The resistor R8 in the start-up circuit is a JFET according to the structures. The NE5532 datasheet from Texas Instruments contains a circuit diagram that is almost completely similar to the circuit diagram from Signetics. However, a JFET is actually drawn in place of the resistor R8.
Also the diodes are included.
Title: Re: Opamps - Die pictures
Post by: exe on February 17, 2023, 11:20:10 pm
Thank you very much for the explanation, that's right on time: I was recently researching on decompensated opamps and NE5534 was one of the few. There are even less with external compensation.

I somewhat like NE5532/NE5534. They, however, have quite some input current (200nA typ, I'll measure it and report). It also looks like their open-loop gain isn't that high (onsemi reports 50000, which is a shame  ;D ). But they are cheap. However, it looks like LM4562 is a better op amp, as it offers more slew rate, GBW, open loop gain, input bias current and doesn't cost a fortune (hello, OPA827).

The difference in datasheets amuses me. The one from TI has just three plots plus generic info about opamps. Onsemi's has more plots, but no application information. The one from Signetics is much more useful. Like, it discusses how to make 5534 unity-gain stable. And it's not just about whacking in a 22pf compensation cap, but designing a proper lead-lag compensator to preserve slew rate.

Links to datasheets:
- Signetics: http://www.elektronikjk.com/elementy_czynne/IC/SE5532A.pdf (http://www.elektronikjk.com/elementy_czynne/IC/SE5532A.pdf)
- Onsemi: https://www.onsemi.com/pdf/datasheet/ne5532-d.pdf (https://www.onsemi.com/pdf/datasheet/ne5532-d.pdf)
- TI: https://www.ti.com/lit/ds/symlink/ne5532.pdf (https://www.ti.com/lit/ds/symlink/ne5532.pdf)

Some entertaining reading for sesquipedalian librocubicularists:
- http://nwavguy.blogspot.com/2011/08/op-amp-measurements.html (http://nwavguy.blogspot.com/2011/08/op-amp-measurements.html)
- https://www.nanovolt.ch/resources/ic_opamps/pdf/opamp_distortion.pdf (https://www.nanovolt.ch/resources/ic_opamps/pdf/opamp_distortion.pdf)
Title: Re: Opamps - Die pictures
Post by: Noopy on February 18, 2023, 04:19:38 am
Those numbers like "6663A" were different on my two dice but I couldn't see any other difference. I'm not sure if they are die versions or maybe location of the die on the wafer.

It seems you are right. My old NE555 all show "1000" (https://www.richis-lab.de/555_6.htm (https://www.richis-lab.de/555_6.htm)). In the first view it looks like it´s a design name. The first few are all named 1000. But the 1973 one and the 1976 one are different!
But what is the number telling us then? I doesn´t look like the location on the wafer to me.


The transistor T16 seems to prevent saturation effects. If the voltage at the collector of T17 drops too far, T16 becomes conductive and consequently reduces the modulation of T13 and thus also of T17.
That's also the role of the second emitter of T10 - preventing saturation of T12. In normal operation its Vbe is zero.

You are right, thanks!  :-+


In the upper part of the first differential amplifier there is a significant difference to the schematic. Between the collector resistors R1/R2 and the positive supply two series connected diodes are integrated (DR). The purpose of these diodes remains unclear. These diodes are not integrated in the NE5534.
As far as I understand, NE5532 reduces its gain by running the input stage at lower current than NE5534. This allows unity gain stability without increasing compensation caps and die area. Other consequences are lower bias current and worse voltage noise.

These diodes provide additional voltage drop to establish proper bias of the second stage, whose operating current depends on common mode voltage at T8,T9 bases.

I agree! Unfortunately I didn´t find an obvious option to reduce the current.


The resistor R8 in the start-up circuit is a JFET according to the structures. The NE5532 datasheet from Texas Instruments contains a circuit diagram that is almost completely similar to the circuit diagram from Signetics. However, a JFET is actually drawn in place of the resistor R8.
Also the diodes are included.

Interesting! It seems I had an old datasheet.
I will add that information.
Thank you for your support!  :clap:
Title: Re: Opamps - Die pictures
Post by: Noopy on February 18, 2023, 05:11:38 am
(https://www.richis-lab.de/images/Opamp/70x10.jpg)

I´m not sure about that capacitor!  :-// :-// :-//

V+ is connected with the buried collector (red). Optical that could be the base too but electrical that would make no sense.

The metal layer is connected with something in the upper area (cyan). Looking at the edges that has to be the collector too. Of course that doesn´t make sense.  :-//

The metal layer is connected to something through "windows". I assume the first window is in the emitter area. I assume the second window is the base layer. The innermost square is the via through the oxide. All in all the metal layer contacts the collector area.  :-//

=> Everything is connected to the collector, nice!  |O

I´m not sure whether there is a emitter layer but without one the structure doesn´t make more sense.  :-//

Any ideas?
Title: Re: Opamps - Die pictures
Post by: magic on February 18, 2023, 08:21:20 am
I agree! Unfortunately I didn´t find an obvious option to reduce the current.
R3 value should be higher than in NE5534.
It looks like NE5532 and NE5533 were designed together to use the same silicon with different metal. Those resistor strips would be connected differently in NE5533 and the original NE5534 was likely different altogether.

Old Raytheon databooks show resistor values and this resistor is different between RC5534 and RC5532.
They also show no diodes above R1/R2, but I'm pretty sure it's an error and RC5532 had them too.

Also the diodes are included.
Interesting! It seems I had an old datasheet.
I suspect you looked at TI NE5534 datasheet, which has no diodes of course.

I´m not sure about that capacitor!  :-// :-// :-//
On TI from Zeptobars it looks like this:

metal layer: signal, connected through the trace coming from top left
a blue layer under the metal, likely a special dielectric
violet emitter layer: VCC, connected at the first DR diode anode
pink base layer: signal, connected through the "windows", which are holes in dielectric and emitter layers
pink-brown collector layer: VCC, connected through the emitter layer at the first DR diode and maybe in other places

TI NE5532 schematic shows almost exactly this connection, but the collector is shown shorted to the base. That's obviously an error, it's shorted to the emitter.

edit
AFAIK similar capacitors were used in OP27 and derived chips, maybe in OP07 too.
This is Linear's schematic symbol for it:
(https://www.eevblog.com/forum/projects/opamps-die-pictures/?action=dlattach;attach=1719323;image)
Title: Re: Opamps - Die pictures
Post by: magic on February 18, 2023, 10:54:21 am
Those numbers like "6663A" were different on my two dice but I couldn't see any other difference. I'm not sure if they are die versions or maybe location of the die on the wafer.

It seems you are right. My old NE555 all show "1000" (https://www.richis-lab.de/555_6.htm (https://www.richis-lab.de/555_6.htm)). In the first view it looks like it´s a design name. The first few are all named 1000. But the 1973 one and the 1976 one are different!
But what is the number telling us then? I doesn´t look like the location on the wafer to me.
Plot twist: one of my dice is 5663A and I think that yours is also 5663A, not 6663A. The first digit looks different than the two 6 in the middle, the top left corner is sharper.

But my other die is 3992A :-//
Title: Re: Opamps - Die pictures
Post by: David Hess on February 18, 2023, 06:35:37 pm
AFAIK similar capacitors were used in OP27 and derived chips, maybe in OP07 too.
This is Linear's schematic symbol for it:

That has come up before.  To me it suggests a "charge storage" transistor structure, although I only know of examples which are PNP.
Title: Re: Opamps - Die pictures
Post by: Noopy on February 18, 2023, 08:26:08 pm
R3 value should be higher than in NE5534.
It looks like NE5532 and NE5533 were designed together to use the same silicon with different metal. Those resistor strips would be connected differently in NE5533 and the original NE5534 was likely different altogether.

I agree. R3 of NE5532 should be twice as high as R3 of the NE5534. I didn´t see a 1:2 option but this R3 with its value R+1/3R can be stripped down to 2/3R which is half of the NE5532 value. A little strange that there is no 2R : R option but it seems they needed a R3 with a little more resistance...


I´m not sure about that capacitor!  :-// :-// :-//
On TI from Zeptobars it looks like this:

metal layer: signal, connected through the trace coming from top left
a blue layer under the metal, likely a special dielectric
violet emitter layer: VCC, connected at the first DR diode anode
pink base layer: signal, connected through the "windows", which are holes in dielectric and emitter layers
pink-brown collector layer: VCC, connected through the emitter layer at the first DR diode and maybe in other places

TI NE5532 schematic shows almost exactly this connection, but the collector is shown shorted to the base. That's obviously an error, it's shorted to the emitter.

edit
AFAIK similar capacitors were used in OP27 and derived chips, maybe in OP07 too.
This is Linear's schematic symbol for it:
(https://www.eevblog.com/forum/projects/opamps-die-pictures/?action=dlattach;attach=1719323;image)

Ah, there is a thin dielectricum! I missed that, thought there is just the normal oxide layer. Now that makes much more sense.
And now I think the TI schematic is correct (talking about my pictures):
V+ connects the capacitor through the emitter doping. Strange for me but makes sense in the big picture.
With the new informations the "windows" under the metal layer are cut into the dielectricum and in the emitter area. That means the metal layer contacts the base area.
At the upper edge the metal layer contacts the collector. That means base and collector are connected and the pn capacitor is between base and emitter.
 :-+
Title: Re: Opamps - Die pictures
Post by: sansan on March 03, 2023, 04:02:31 pm
In the upper part of the first differential amplifier there is a significant difference to the schematic. Between the collector resistors R1/R2 and the positive supply two series connected diodes are integrated (DR). The purpose of these diodes remains unclear. These diodes are not integrated in the NE5534.
Maybe this?
[attach=1]
From NJM5532DD datasheet
Title: Re: Opamps - Die pictures
Post by: magic on March 04, 2023, 08:34:14 am
This is unrelated.

The parasitic diodes between Vin and V+ are the BC junction of the input transistor (Q1 or Q2) and the junction between the diffused collector resistor (R1 or R2) and its isolation island. They are shown as PNPs because the P substrate can collect minority carriers injected from the P element into its corresponding N isolation island. The resistor represents substrate resistance. The parasitic NPN's base is the substrate, collector is the Q1/Q2 isolation island and its emitter must be some other nearby isolation island connected to ground through a pair of transistors. My bet is on C2, which is close to the input pair in Signetics, TI and Philips and solidly grounded to the V- pin through BE junctions of the VAS transistors.

The way they draw this parasitic circuit looks like it may be capable of latchup.
Title: Re: Opamps - Die pictures
Post by: Noopy on March 08, 2023, 09:04:42 am
I have some updates for the AMD AM685. The AMD Linear and Interface Data Book contains some interesting information.


(https://www.richis-lab.de/images/Opamp/69x03.jpg)

The quality of the schematic is a little better and here we have the link between the resistors R4 and R21 that is missing in the datasheet.


(https://www.richis-lab.de/images/Opamp/69x07.jpg)

The transistors are described in detail in the Linear and Interface Data Book. In the input stage, the transistors have to behave as equally as possible. In addition, a high amplification factor and a high cutoff frequency are necessary.

To get high switching speeds, one has tried to keep the parasitic capacitances and the resistances low. These two goals require partially counterproductive measures. The epi collector layer has been made very thin. This reduces the size of the lateral contact areas with the substrate and thus the collector-substrate capacitance. Furthermore, the epi-layer was only slightly doped, which reduces the base-collector and the collector-substrate capacitances. At the same time unfortunately, this increases the collector resistance. The so-called n+ sinker and the low-lying collector feed line ensure that the collector is connected with the lowest possible resistance. Since this highly doped area is only locally below the active area, it does not increase the collector-substrate capacitance too much.

To reduce the base-collector capacitance, the base region was just lightly doped too. Since this increases the base resistance, two base contacts were integrated to the right and left of the emitter. Highly doped regions within the low-doped active base layer further reduce base resistance.

According to the Linear and Interface Data Book, the emitter is 25,4µm x 6,35µm. The tolerance of these structures is 0,25µm. The size is a compromise between good high frequency characteristics, which require a small emitter, and the need to create transistors with as similar characteristics as possible, which is more difficult with smaller structures due to tolerances.

At the right end, the structure features a Schottky diode created by direct metal contact with the weakly n-doped collector region. Integrating the diode into the transistor reduces the area required for the circuit.

Above the sectional view, transistor Q4 is shown. According to the schematic, this is a normal transistor. The die shows that actually three emitters were integrated. The remaining areas can also be seen clearly. The n+ sinker, which contacts the buried collector supply line, is very wide in the above transistor and thus offers a certain variability in contacting and line routing.


(https://www.richis-lab.de/images/Opamp/69x08.jpg)

The Linear and Interface Data Book also shows the metal layer of the AM685. You can see that the design has been revised once. The most striking feature is the smiley in the lower right corner.


(https://www.richis-lab.de/images/Opamp/69x09.jpg)

If you superimpose the printed metal layer and the die available here, you can see that areas within the circuit have been redesigned too.


(https://www.richis-lab.de/images/Opamp/69x10.jpg)

The more extensive connection of the substrate can be seen very clearly. Even though only the metal layer is shown for the first revision, it can be said that the contacting of the substrate only took place next to the bondpad (cyan). In the present design, the distribution of the V- potential has been made wider and connected to the substrate over a large area at three additional locations (red). This ensures that free charge carriers in the substrate are drained quickly and do not negatively influence the circuit.


(https://www.richis-lab.de/images/Opamp/69x06.jpg)

An interesting difference from the schematic and КP597CA1 is the absence of diodes D1 and D2. The transistors Q3/Q4 contain the areas and contacts for the diodes, but they are not cross-connected. The metal layer of the first revision shows that there the two diodes were still integrated in the circuit.

The diodes D1/D2 suppress saturation effects and thus accelerate the switching of the comparator. However, in the Linear and Interface Data Book AMD points out that it meant a certain effort to manufacture the Schottky diodes in the necessary quality. After all, in the input stage the two branches have to behave as equally as possible. In addition, the diodes bring parasitic capacitances into the system. Perhaps the transistors were fast enough even out of saturation mode that it was more advantageous to do without the diodes.


(https://www.richis-lab.de/images/Opamp/69x11.jpg)

(https://www.richis-lab.de/images/Opamp/69x12.jpg)

Some of the resistors have enlarged contact areas on one side, which make it possible to vary the effective resistance values by moving the vias (red).
In comparison to the first revision of the metal layer, it can be seen that here the resistor R9 has been shorted (blue). This changes the bias of the output stage.


https://www.richis-lab.de/Opamp65.htm (https://www.richis-lab.de/Opamp65.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: David Hess on March 08, 2023, 05:02:12 pm
The diodes D1/D2 suppress saturation effects and thus accelerate the switching of the comparator. However, in the Linear and Interface Data Book AMD points out that it meant a certain effort to manufacture the Schottky diodes in the necessary quality. After all, in the input stage the two branches have to behave as equally as possible. In addition, the diodes bring parasitic capacitances into the system. Perhaps the transistors were fast enough even out of saturation mode that it was more advantageous to do without the diodes.

If a diode structure is used, then its leakage (even at zero volts) also reduces the gain of a high impedance output from a differential pair so transistor junctions are used instead, but I do not think that would matter here with a 300 ohm load and even schottky diodes could be used.

It is not usually shown in the schematics, but comparators have schottky diodes used as baker clamps on selected transistors to prevent saturation.  Operational amplifiers lack these and other anti-saturation measures leading to long recovery time.
Title: Re: Opamps - Die pictures
Post by: Noopy on March 23, 2023, 03:42:59 pm
(https://www.richis-lab.de/images/Opamp/71x01.jpg)

You can find hardly any information about the Signetics NE1037. Linear Technology mentions the NE1037 in the "Linear Databook Supplement" from 1988 and refers to the LT1037 as an alternative. As will be shown in a moment, this is indeed an LT1037 that Signetics seems to have adopted. The LT1037 is advertised as a precision opamp that is very fast (60MHz) while offering low noise (4.5nV/√Hz, 10Hz) and low offset voltage (<110µV).


(https://www.richis-lab.de/images/Opamp/71x03.jpg)

(https://www.richis-lab.de/images/Opamp/71x02.jpg)

The dimensions of the die are 2,5mm x 2,1mm. It is the typical topology with the input stage integrated at the left edge centered around the horizontal axis. With the output stage centered on the right edge, this guarantees that the power dissipation there affects the two branches of the input stage as symmetrically as possible.

The capacitors take up a lot of surface area on the die. Particularly noticeable is the upper capacitor, of which only a fraction of the area is used. One can assume that this design is used for at least one other opamp, and there a much larger capacitor area is incorporated into the circuit. In Linear Technology's case, this is almost certainly the LT1007, which is listed with the LT1037 on the same datasheet. The LT1037 is stable just at amplification factors greater than 5, but offers a cutoff frequency of 60MHz and a slewrate of 15V/µs. The LT1007 can also be used as a voltage follower, the cutoff frequency is 8MHz and the maximum slewrate is 2,5V/µs.


(https://www.richis-lab.de/images/Opamp/71x04.jpg)

The bottom edge shows that Linear Technology's design dates back to 1983.


(https://www.richis-lab.de/images/Opamp/71x06.jpg)

Next to the Linear Technology logo are the numbers 37, which most likely stands for LT1037. The LT1007 simply uses a different metal layer. I don´t know that the I can tell us.


(https://www.richis-lab.de/images/Opamp/71x07.jpg)

(https://www.richis-lab.de/images/Opamp/71x05.jpg)

ZE and GE could be abbreviations of the developers. Next to the letters GE, a smiley has made it onto the die.


(https://www.richis-lab.de/images/Opamp/71x08.jpg)

The two input transistors are doubled and cross-connected so that thermal gradients affect both branches of the opamp as equally as possible. To the right, the following elements are also arranged symmetrically around the center axis.


(https://www.richis-lab.de/images/Opamp/71x09.jpg)

The structure in the lower left corner is unusual. It seems to be a capacitor like in the NE5532 (https://www.richis-lab.de/Opamp66.htm (https://www.richis-lab.de/Opamp66.htm)), which additionally uses the capacitance of the base-emitter junction.

At the lower edge of the picture you can see the diodes which limit the voltage between the inputs of the opamp.


(https://www.richis-lab.de/images/Opamp/71x10.jpg)

In the upper left corner there are some small resistors which can be configured via several testpads and fuses. They allow to adjust the offset voltage of the opamp during manufacturing. The design of these resistors in the supply of the input amplifier strongly reminds of the LT1012 (https://www.richis-lab.de/Opamp56.htm (https://www.richis-lab.de/Opamp56.htm)).


(https://www.richis-lab.de/images/Opamp/71x11.jpg)

The LT1037 offers two pins to further adjust the offset voltage. This leaves only one bondad, which at first glance cannot be assigned to any function. The detail shows that the bondpad in the upper right corner just supplies the powerstage of the opamp. The bondpad next to it seems to be isolated from it and feeds the positive supply potential to the rest of the circuit.


https://www.richis-lab.de/Opamp67.htm (https://www.richis-lab.de/Opamp67.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on March 23, 2023, 08:04:37 pm
Interesting find. The die has LT trademarks all over it but the package and markings are typical Signetics.
I guess Signetics packaged the chip and Linear designed the masks, but not sure who fabbed the die.

LT1007/LT1037 are Linear's improved substitutes for OP27/OP37. The 37 are decompensated, as you noted, hence much smaller capacitors.
GE is probably George Erdi, who originally designed these PMI parts (also OP07) and later moved to Linear and designed chips for them.
His name may also appear on LT1001, which was Linear's answer to OP07.

The capacitor likely uses the same structure previously discussed in the context of NE5534.
Also LT1028/LT1128/LT1115, where it looks visually similar to this one. LT1115 is on Zeptobars.

BTW, I think I previously said that OP27/37 also used such capacitor. I was wrong, your OP27 teardown shows only ordinary MOS caps.
Title: Re: Opamps - Die pictures
Post by: Noopy on April 13, 2023, 03:22:09 am
(https://www.richis-lab.de/images/Opamp/72x01.jpg)

(https://www.richis-lab.de/images/Opamp/72x02.jpg)

(https://www.richis-lab.de/images/Opamp/72x03.jpg)

From this component the labelling has been removed. As we will see, it is a TLC074 from Texas Instruments. The opamp family TLC07x is the successors of the TL07x series. Most of the specifications have been improved. The bandwidth is 10MHz, with a slew rate of up to 16V/µs. Expect a maximum offset voltage of 1mV, typically drifting at 1,2µV/°C. Typical of more modern designs, the supply voltage range has been lowered. While the TL07x opamps allow 7 - 36V, 4,5 - 16V is specified for the TLC07x variants. The outputs can drive more than 50mA.


(https://www.richis-lab.de/images/Opamp/72x04.jpg)

The TLC07x family offers several variants, including housings with improved thermal conductivity. The TLC074 contains four opamps. The TLC075 variant additionally offers the possibility to switch off the operational amplifiers in pairs.


(https://www.richis-lab.de/images/Opamp/72x05.jpg)

(https://www.richis-lab.de/images/Opamp/72x06.jpg)

The dimensions of the die are 2,4mm x 1,4mm. According to the datasheet, it was manufactured with the LBC3 BiCMOS process.

The areas of the four opamps are clearly visible. On closer inspection, one can identify where the bondpads for the supply voltage, the inputs and the outputs are placed. There are two unused bondpads in the right-hand area.


(https://www.richis-lab.de/images/Opamp/72x07.jpg)

(https://www.richis-lab.de/images/Opamp/72x08.jpg)

The designation TLC075 is found on the die. That is plausible so far. The same designs are obviously used for the TLC074 and the TLC075, only the shutdown inputs of the TLC074 are not led to the outside. The circuit dates back to 1999, which is consistent with the first revision of the datasheet.


(https://www.richis-lab.de/images/Opamp/72x09.jpg)

The TLC074 at hand was obviously massively overloaded. This is most clearly visible in the opamp in the upper right corner. In the large, regular structures, two areas are blackened. But all other circuit parts are also discoloured over a large area.


https://www.richis-lab.de/Opamp68.htm (https://www.richis-lab.de/Opamp68.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on April 15, 2023, 03:24:21 am
(https://www.richis-lab.de/images/Opamp/73x01.jpg)

(https://www.richis-lab.de/images/Opamp/73x02.jpg)

The labelling of this component has been ground off. As will become apparent, it is the dual opamp TLC2262 from Texas Instruments. The datasheet specifies a supply voltage range of +/-2,2V to +/-8V, whereby single supply is also possible. The current consumption is typically 400µA. The TLC2262 offers a rail-to-rail output. Absolute Maximum Ratings specify 50mA as the output current. Typically, the currents are much lower. If one approaches the supply potentials, the maximum possible current also drops sharply.

The relatively low noise of 40nV/√Hz (10Hz) or 12nV/√Hz (1kHz) is emphasised. The offset voltage is typically 300µV with a temperature drift of 2µV/°C. At room temperature, a bias current of 0,5pA can be expected. The low current consumption of the opamp is noticeable in the speed. The bandwidth is only 0,71MHz. The maximum possible slewrate is typically 0,55V/µs.


(https://www.richis-lab.de/images/Opamp/73x03.jpg)

The datasheet contains a circuit diagram that shows a very clear circuit. The circuit section Q14-Q17 on the far right generates a reference voltage that ensures that Q3 and Q6 behave like current sources. The differential amplifier Q1/Q4 at the input works against the current mirror Q2/Q5.

The output of the differential amplifier directly controls the lowside transistor Q13 at the output. R5/C1 limits the frequency response and thus stabilises the circuit. Q11 represents a current limitation with R1.

The connection of the highsidetransistor Q12 and the transistors Q7-Q10 seems illogical, but it becomes clearer in the following if you look at the circuits of the related opamps.


(https://www.richis-lab.de/images/Opamp/73x08.jpg)

In addition to the TLC2262, Texas Instruments also offers the TLC2252 and the TLC2272. The TLC2252 typically consumes only 70µA, but also offers a slewrate of just 0,12V/µs and a bandwidth of 0,2MHz. The TLC2272, on the other hand, draws 2,2mA and thus enables a slewrate of 3,6V/µs and a bandwidth of 2,18MHz. The TLC2262 represents the compromise of both types: 400µA / 0,55V/µs / 0,82MHz. With increasing current consumption, the noise of the opamp is also reduced.

The datasheets of all three opamps contain circuit diagrams that only differ in the wiring of the transistors Q9 and Q12. In the TLC2272, transistors Q12/Q13 form a push-pull output stage. Q12 is controlled from the differential amplifier at the input, whose signal is transmitted to the output stage via transistors Q7-Q10. Q9 and Q12 form a current mirror here.

In the TLC2262, transistor Q9 is isolated from the rest of the circuit. Since the control of Q12 lacks any pull-up structure, Q12 behaves like a current source in the TLC2262. Consequently, the output stage operates in class A mode. The maximum possible current change at the output is reduced accordingly, but the current consumption of transistor Q9 is saved.

In the TLC2252, Q9 is integrated into the circuit again. The resistor R6 has been added. This results in the same function as in the TLC2272, but with a reduced current. The combination of the more efficient class B operation of the output stage with the reduced current through Q9 obviously results in a minimal current consumption. Now, however, the highsidetransistor must be charged with the low current of Q9, which significantly reduces the speed of the opamp.

The advantage of these modifications is that one just has to make small changes to the circuit to be able to represent three different opamps.


(https://www.richis-lab.de/images/Opamp/73x04.jpg)

(https://www.richis-lab.de/images/Opamp/73x05.jpg)

The dimensions of the die are 2,3mm x 1,6mm. It is manufactured using the so-called "Advanced LinCMOS" process. A more detailed analysis of the circuit is difficult due to the small structure sizes and the two metal layers.

The dichotomy of the die is clearly visible. The inputs with their extensive protective structures can also be clearly identified. The large structures in the middle of the die appear to be the transistors of the input stage. On the right and left edges there are three testpads each, which are clearly used to adjust resistors. Above them, the offset voltage is most likely adjusted via resistors R3/R4.

The function of the central testpad on the upper edge remains open. Since it apparently influences both opamps, it could be that the bias is adjusted over it.


(https://www.richis-lab.de/images/Opamp/73x07.jpg)

The die is marked with TLC2262. In principle, one cannot be sure in such a case whether it is not just a basic variant that can also be configured as TLC2252 or TLC2272. Most likely, however, it is a TLC2262 and the variants TLC2252 and TLC2272 are represented by variations of the metal layer, which then can be given their own designations. It hardly seems conceivable that the one testpad is sufficient to switch between the three different circuit variants.


(https://www.richis-lab.de/images/Opamp/73x06.jpg)

The design dates from 1998. In the lower left corner at the output bondpad, the output stage can be seen. The highside transistor is surprisingly small.


https://www.richis-lab.de/Opamp69.htm (https://www.richis-lab.de/Opamp69.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on April 15, 2023, 08:41:40 am
I don't believe this schematic.

The moment Q10 turns on to any degree for any reason, it grounds Q12 gate and then the gate is left charged to ground potential.
Might as well wire the gate to ground permanently.
Title: Re: Opamps - Die pictures
Post by: Noopy on April 15, 2023, 08:46:39 am
I agree with you but assume it is done that way to make it as easy as possible to change between the three opamps.
Just some minor changes around Q9 and you get the one or the other opamp... :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on April 17, 2023, 03:41:27 pm
(https://www.richis-lab.de/images/Opamp/74x01.jpg)

The marking of this component has been ground off (again  ;D). As will be shown, it is a TLE2072 from Texas Instruments. The TLE207x family is listed under the sounding name "Excalibur Low-Noise High-Speed JFET-Input Operational Amplifier". The datasheet presents them as an upgrade to the TL07x opamps.

The TL2072 achieves a slewrate of typically 40V/µs and a bandwidth of 10MHz. The circuit is rated at supply voltages between +/-5V and +/-19V and then typically draws 2,9mA. Due to the Excalibur manufacturing process, the voltage noise is only 48nV/√Hz (10Hz) and 12nV/√Hz (1kHz) respectively. If this characteristic value is less critical, an opamp from the TL208x series can be used. The offset voltage of the better bin with index A is typically 0,7mV and drifts with 2,4µV/°C. A variant exists that is approved for an operating temperature range of -55°C to 125°C.

The TLE2072 contains two opamps. The TLE2071 and TLE2074 offer one and four operational amplifiers, respectively.


(https://www.richis-lab.de/images/Opamp/74x02.jpg)

The TLE2072 is a BiFET opamp. It therefore combines JFET transistors with classic bipolar transistors. The schematic in the datasheet looks very complex, but a large part of the circuit is only used to generate constant current sources (blue).

In the center we see the input amplifier (yellow). Interesting are the two JFETs Q15 and Q19. They ensure that an overdrive of an input does not have too negative an effect on the behavior. If the potential at one of the inputs drops, then the associated transistor (Q13 or Q20) allows more current to flow through its path. However, if the potential drops to the point where the junction of the transistor becomes conductive, then current flows across it and a phase reversal occurs at the output of the opamp. Transistors Q15 and Q19 ensure that in such an operating state a similar current also flows from the other branch and the basic function of the differential amplifier is not completely cancelled out.

Transistor Q16 compensates saturation effects that can occur if the power amplifier's overcurrent protection drains current from the differential amplifier. At the bottom of the differential amplifier is a current mirror whose frequency response has been extensively limited with capacitors C2 and C4. At this point, the TLE2071 offers the possibility to externally adjust the offset voltage. Capacitor C6, which limits the frequency response of the complete opamp, is fed back from the output to the input amplifier.

The differential amplifier is followed by the voltage amplifier stage (purple). The voltage amplification is done by Q26. Q22 is a buffer amplifier.

The transistors Q24/Q25 (gray), connected as diodes, generate a certain voltage drop and thus a certain quiescent current through the complementary output amplifier (red). In the case of the highsidetransistor, the overcurrent protection (green) directly sinks the base current. In the case of the lowside transistor, the circuit reduces the output current of the input amplifier.


(https://www.richis-lab.de/images/Opamp/74x05.jpg)

The datasheet documents the number of components used in the variants with one, two and four amplifiers. The numbers reveal that the two opamps in the TLE2072 share the bias circuit. In the TLE2074, on the other hand, the TLE2072 was merely doubled up.


(https://www.richis-lab.de/images/Opamp/74x03.jpg)

(https://www.richis-lab.de/images/Opamp/74x04.jpg)

The dimensions of the die are 2,3 x 2,0mm. The symmetry of the circuit can clearly be seen, as well as the deviating circuit part in the right area, which contains the common bias circuit.


(https://www.richis-lab.de/images/Opamp/74x11.jpg)

In the datasheet of the TLE208x the metal layers of the opamps are shown. These pictures confirm that the TLE207x and the TLE208x contain the same die and just have been binned.


(https://www.richis-lab.de/images/Opamp/74x07.jpg)

The design obviously dates from 1994. Some of the masks used in the manufacturing process can be seen on the top edge in the scribe line.


(https://www.richis-lab.de/images/Opamp/74x08.jpg)

The EX 2072B designation suggests that the circuit is a second revision.


(https://www.richis-lab.de/images/Opamp/74x06.jpg)

The layout of the circuit parts is rather unusual. The input transistors are located in the center. To the left is the current mirror of the input stage with the large capacitors integrated there. To the right, directly next to the input transistors, the two large current sources are integrated. Further to the right is the output stage.


(https://www.richis-lab.de/images/Opamp/74x09.jpg)

(https://www.richis-lab.de/images/Opamp/74x12.jpg)

The input transistors are doubled and cross-connected so that thermal gradients do not have too strong an effect. Directly to the left of the input transistors are two elements that resemble capacitors. In fact, they are the JFETs that become conductive when the potentials at the inputs get too negative.


(https://www.richis-lab.de/images/Opamp/74x10.jpg)

Two testpads are integrated on the left edge. They allow to adjust the emitter resistors of the current mirror and thus the offset voltage of the input stage via Zener fuses.


https://www.richis-lab.de/Opamp70.htm (https://www.richis-lab.de/Opamp70.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Kleinstein on April 17, 2023, 06:23:00 pm
The TLE207x have a strange effect when the output is driven hard to the negative side. Under this conditions the supply current goes up quite a bit (up to some 20 mA). At least this strange behavior is shown in the data-sheet.
So one should avoid using this type when the neg. side saturation can happen regularly for a longer time.
Title: Re: Opamps - Die pictures
Post by: exe on April 17, 2023, 07:23:55 pm
I also noticed a strange thing: on Figure 14 they plot "INPUT BIAS CURRENT vs TOTAL SUPPLY VOLTAGE". I don't get it, after 20V of total supply voltage input bias goes to the roof?
Title: Re: Opamps - Die pictures
Post by: T3sl4co1l on April 17, 2023, 07:37:15 pm
A typical JFET effect, hot carriers in the channel increase gate leakage.  A cascode could alleviate that, at some expense of headroom near the negative rail.

Tim
Title: Re: Opamps - Die pictures
Post by: magic on April 17, 2023, 08:35:53 pm
Unusually, the schematic shows compensation (C6) being connected to the output stage rather than Q26 collector. This includes those emitter followers in the feedback loop of the second stage. High frequency performance ought to be better, but there is higher risk of instability due to phase shit of the output stage.

The TLE207x have a strange effect when the output is driven hard to the negative side. Under this conditions the supply current goes up quite a bit (up to some 20 mA).
It's not clear if anything seriously limits how much base current Q22 can feed into Q26. In TL072, a diode forward biases and allows Q26 to steal base current from Q22.
Title: Re: Opamps - Die pictures
Post by: Noopy on April 18, 2023, 03:23:08 am
Thanks for all the input, very interesting!  :-+


Unusually, the schematic shows compensation (C6) being connected to the output stage rather than Q26 collector. This includes those emitter followers in the feedback loop of the second stage. High frequency performance ought to be better, but there is higher risk of instability due to phase shit of the output stage.

It´s amazing how small C6 is and how big the other capacitors are.
Title: Re: Opamps - Die pictures
Post by: Noopy on April 18, 2023, 04:00:11 am
(https://www.richis-lab.de/images/Opamp/74x14.jpg)

Nice!  ;D ;D ;D
Title: Re: Opamps - Die pictures
Post by: Noopy on April 19, 2023, 07:55:37 pm
(https://www.richis-lab.de/images/Opamp/73x08.jpg)

With a second thought about the TLC22x2 my explanation was not completely right. The output stages would probably consume more current going from the TLC2272 to the TLC2252 not less.
In addition with the difference in slewrate and noise voltage there has to be a variation of the current in the input stage. Are the differences in the output stage incorrect or additional differences beside the current in the input stage? For me that is unclear...  :-//
Title: Re: Opamps - Die pictures
Post by: Noopy on April 20, 2023, 09:04:25 am
I have sorted my opamp section:

Small-Signal-Opamps (Bipolar/JFET/MOSFET):
https://www.richis-lab.de/Opamp.htm (https://www.richis-lab.de/Opamp.htm)

Power-Opamps:
https://www.richis-lab.de/Opamp_pwr.htm (https://www.richis-lab.de/Opamp_pwr.htm)

Instrumentation amplifier (more coming soon):
https://www.richis-lab.de/Opamp_instr.htm (https://www.richis-lab.de/Opamp_instr.htm)

Comparators:
https://www.richis-lab.de/Opamp_comp.htm (https://www.richis-lab.de/Opamp_comp.htm)

Voltage Follower (don´t know if there will ever come more):
https://www.richis-lab.de/Opamp_vfol.htm (https://www.richis-lab.de/Opamp_vfol.htm)
Title: Re: Opamps - Die pictures
Post by: iMo on April 20, 2023, 10:53:06 am
Still no choppers?  :)
Title: Re: Opamps - Die pictures
Post by: Noopy on April 20, 2023, 11:04:30 am
Still no choppers?  :)

So much to do....
Would a LTC1051 be ok?
Title: Re: Opamps - Die pictures
Post by: iMo on April 20, 2023, 11:32:13 am
Just asking, it is not a request  :D
Any chopper will do, indeed, as we do not any yet, afaik..
Title: Re: Opamps - Die pictures
Post by: Noopy on May 07, 2023, 08:56:34 am
(https://www.richis-lab.de/images/Opamp/75x01.jpg)

The OPA604 seen here was purchased via Ebay. The seller has already sold a three-digit number of these opamps. The slightly furrowed surface and the somewhat clumsy Burr-Brown logo arouse suspicion.


(https://www.richis-lab.de/images/Opamp/75x05.jpg)

In the close-up, the lettering appears somewhat faint. A layer is coming off at the side edge. Most likely, the package was sanded down and painted before the new lettering was applied.


(https://www.richis-lab.de/images/Opamp/75x02.jpg)

The OPA604 is an opamp optimized for audio applications. It has JFET inputs and, according to the datasheet, is balanced with a laser.


(https://www.richis-lab.de/images/Opamp/75x03.jpg)

(https://www.richis-lab.de/images/Opamp/75x04.jpg)

The dimensions of the die that can be found in this part are 0,83mm x 0,69mm. It is certainly not an OPA604. Two opamps are integrated in this circuit. At the lower edge are the input transistors, which are PNP transistors. In the upper area you can see the large output transistors.

The design strongly reminds of the fake NE5534 (https://www.richis-lab.de/Opamp11.htm (https://www.richis-lab.de/Opamp11.htm)). As described there, the design is similar to the Raytheon RC4558N.


(https://www.richis-lab.de/images/Opamp/75x06.jpg)

(https://www.richis-lab.de/images/Opamp/75x07.jpg)

There are two symbols on the die that cannot be assigned. One symbol seems to represent the characters P004. The other symbol seems similar to a snail shell.  :-//


https://www.richis-lab.de/Opamp71.htm (https://www.richis-lab.de/Opamp71.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on May 07, 2023, 05:12:58 pm
Chances of scoring genuine Burr-Brown chips on auction sites are low. Too much audiophool demand for them.

Same logo was found on an LM324 pretending to be TL074 on eBay and LM358 sold as OP07 on AliExpress. See here (https://www.eevblog.com/forum/beginners/opamp-input-offsets-working-in-the-opposite-direction-to-what-i-expect/msg2680314/#msg2680314) and my image a few posts below.

Regarding actual OPA604, there is further information about internals in two patents mentioned in the datasheet. This includes the output stage and "distortion rejection circuitry", which is simply a sort of "clever" driver for the P-JFET active load. The FETs are controlled by an NPN differential pair which maintains equal voltage on both sides of the folded cascode. This provides differential cancellation of base width / channel length modulation effects (to some extent), increasing open loop gain and reducing distortion.
Title: Re: Opamps - Die pictures
Post by: Noopy on May 08, 2023, 03:03:36 am
The OPA604 is an interesting device. Probably I will take some pictures of a real one.

This "logo" seems to be wide spread. Would be interesting which company that is.
Title: Re: Opamps - Die pictures
Post by: Noopy on May 20, 2023, 06:56:08 pm
(https://www.richis-lab.de/images/Opamp/62x01.jpg)

[...]


(https://www.richis-lab.de/images/Opamp/62x04.jpg)

[...]


https://www.richis-lab.de/Opamp59.htm (https://www.richis-lab.de/Opamp59.htm)


Someone gave me a hint regarding this strange symbol:
These are the letters dfb which probably stand for Derek F. Bowers, a famous guy working for Precision Monolithics and Analog Devices.

 :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on June 19, 2023, 12:04:44 pm
(https://www.richis-lab.de/images/Opamp/76x01.jpg)

With the A109 the Halbleiterwerk Frankfurt Oder manufactured a variant of the widely used opamp µA709. The B109 was a better bin. The letter C stands for the ceramic package. The datecode AT refers to a production in January 1977.


(https://www.richis-lab.de/images/Opamp/76x02.jpg)

The package consists of two ceramic elements. The mass that connects the two halves is somewhat unevenly distributed. The pins are rusting at the package.


(https://www.richis-lab.de/images/Opamp/76x05.jpg)

(https://www.richis-lab.de/images/Opamp/76x04.jpg)

The edge length of the die is 1,2mm. The unused area around the active area is surprisingly large. Perhaps this was to create a buffer area for the separation process. The irregular edge in the lower right corner shows that the separation process was somehow problematic.


(https://www.richis-lab.de/images/Opamp/76x07.jpg)

(https://www.richis-lab.de/images/Opamp/76x06.jpg)

There are a lot of cracks on the surface of the die. This appears to be damage in the passivation layer. Similar cracks were found on the MAA723 (https://www.richis-lab.de/LM723_04.htm (https://www.richis-lab.de/LM723_04.htm)).


(https://www.richis-lab.de/images/Opamp/76x03.jpg)

A schematic of the A109 can be found in "Halbleiterinformation 117", much of the content of which is also printed in the magazine "Radio Fernsehen Elektronik" (24/1976). The circuit diagram corresponds to the circuit diagram in the datasheet of the LM709.



[...]

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on June 19, 2023, 12:05:47 pm
(https://www.richis-lab.de/images/Opamp/76x08.jpg)

For the A109, part of the mask set has survived. Only the mask of the metal layer and the mask defining the contacts between the metal layer and the active areas are missing.


(https://www.richis-lab.de/images/Opamp/76x09.jpg)

Without more detailed analysis, you can already see the markings that were used to align the masks. These are two points each on the left and right edge (green/yellow), which lie on top of each other when the masks are in place. The green marked points are still visible on the present die, the yellow marked points have been cut off.

The blue marked structure allows to check the alignment of the masks against each other. These are four squares arranged within a larger square. As will be shown, for the masks that introduce an n-doping, the squares are set at the top left and bottom right, while for the p-doping, the squares are open at the bottom left and top right.

In the lower area, another auxiliary structure is shown (cyan). However, only two masks contribute to this structure.


(https://www.richis-lab.de/images/Opamp/76x15.jpg)

The masks make it easier to analyze the structure of the integrated circuit. The starting material is a p-doped substrate. It is protected by a silicon oxide layer. For the sake of clarity, silicon oxide layers are not shown.


(https://www.richis-lab.de/images/Opamp/76x16.jpg)

In a first process step a strong n-doping is introduced into the p-doped substrate. The n-doping later serves as a low-resistance collector feed line under the collector ("buried collector".


(https://www.richis-lab.de/images/Opamp/76x10.jpg)

The mask for the buried collector matches the structures on the present A109. It can be recognized by the optically strongly protruding edges.

The high n-doping is located under each active structure except the PNP transistor T13 at the right edge. This transistor is a substrate transistor, a vertical transistor that uses the p-doped substrate as a collector. Vertical PNP transistors have better characteristics than lateral PNP transistors. But you can use them only if the collector should be connected to the negative supply potential.


(https://www.richis-lab.de/images/Opamp/76x17.jpg)

After inserting the buried collector, a n-doped layer is applied using epitaxy. This layer covers the entire surface of the wafer.


(https://www.richis-lab.de/images/Opamp/76x18.jpg)

At the points where isolated areas are required, p-doping is introduced into the epi-layer. The p-doping extends to the substrate and forms a well that isolates the active regions as long as the substrate has the lowest potential of the circuit.


(https://www.richis-lab.de/images/Opamp/76x11.jpg)

Looking at the mask of the p-doping just described, we see that this not only creates isolated areas for the active elements. The areas under the bondpads are also isolated from the rest of the circuit. Only the bondpad in the lower right corner is an exception. The negative supply potential is transmitted via this bondpad, which is connected to the substrate.

In the active structures, the n-doping of the wells hardly stands out optically. It can be confined via the surrounding structures. In the next step, the isolation frames are widened. This means that the surroundings of the narrow isolation frames do not yet contain the n-doping. The boundary of the n-doping is the edge surrounding the buried collector. Above the buried collector, of course, there is this n-doping too.


(https://www.richis-lab.de/images/Opamp/76x19.jpg)

In the next step, the p-doping is introduced, which, among other things, represents the base layer of the NPN transistors. At the same time, resistors can be represented with the base doping. As will be shown in a moment, this process step also strengthens the lateral isolation of the active areas.


(https://www.richis-lab.de/images/Opamp/76x12.jpg)

The mask of the p-doping forms the base areas of the NPN transistors, collector and emitter areas of the PNP transistors and the resistors. In the NPN transistors, the base areas can be seen relatively well, since they are only overlaid by the smaller emitter area.

The mask pattern shows that the p-doping also reinforces the isolation around the active areas. This means that not only the narrow frame structures are p-doped, but also the immediate surroundings.

In the lower right corner of the die, one can see that the negative supply is connected to the isolation frame and thus to the substrate too.


(https://www.richis-lab.de/images/Opamp/76x20.jpg)

Finally, a strong n-doping is introduced, which represents the emitter areas. It also forms the contact areas to the collector. A direct contact of the metal layer with the weak n-doping would form a Schottky contact, a diode. In addition, the strong n-doping in the contact area provides lower resistances in the path to the collector.


(https://www.richis-lab.de/images/Opamp/76x13.jpg)

The mask of the strong n-doping has corresponding cutouts where the emitters are located and where collector areas are contacted. On the die, the collector contacts are usually hidden under the metal layer. The emitter areas are deposited by their edges in the innermost part of the transistor structures.

The NPN transistor T10 has a special shape. Together with the transistor T11 T10 serves as a current source for the differential amplifier at the input. Why this shape was advantageous remains unclear. The two transistors must have different base-emitter voltages. Probably this is the reason for the special construction.

Also noticeable are the two PNP transistors T9 and T13. Here the strong n-doping acts as a low impedance base contact. At T13, the vertical PNP transistor, the highly doped area circles around the entire active area to get a very low base impedance.

The large n+ area in the upper right area is a low impedance connection of the well to the positive supply. This is necessary because the highside transistor of the output stage is located in this well. With high currents through this transistor there is the possibility that the potential of the well shifts and the resistors integrated in the same well are influenced.


(https://www.richis-lab.de/images/Opamp/76x22.jpg)

After completion of the active structures, an insulating silicon oxide layer is applied to the entire surface of the wafer. After that contacts to the active area are etched. The mask for this process are missing.


(https://www.richis-lab.de/images/Opamp/76x23.jpg)

A metal layer is then applied over the entire surface of the silicon oxide layer and structured with another mask, which is missing too.

Finally, the entire wafer is covered with a passivation layer that protects the active elements from environmental influences (not shown here). This is probably silicon oxide. On more modern circuits silicon nitride is usually used. Where the bondwires are to contact the metal layer, openings must be etched into the passivation layer. This requires another mask, which is missing too.


(https://www.richis-lab.de/images/Opamp/76x14.jpg)

Instead of the mask for the metal layer, the A109 document contains a kind of a wiring diagram, which shows where the individual elements are located.

Next to the resistor R11 there is a slightly shorter, unused resistor (yellow). By varying the metal position you can use this resistor as R11 or even connect both resistors in parallel. Thus it is possible to adjust the bias of the differential amplifier at the input.


(https://www.richis-lab.de/images/Opamp/76x24.jpg)

(https://www.richis-lab.de/images/Opamp/76x25.jpg)

With the above conclusions, one can assign all structures on the die to their functions.


https://www.richis-lab.de/Opamp72.htm (https://www.richis-lab.de/Opamp72.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on June 20, 2023, 10:37:34 am
(https://www.richis-lab.de/images/Opamp/76x17.jpg)

After inserting the buried collector, a n-doped layer is applied using epitaxy. This layer covers the entire surface of the wafer.


(https://www.richis-lab.de/images/Opamp/76x18.jpg)

At the points where isolated areas are required, p-doping is introduced into the epi-layer. The p-doping extends to the substrate and forms a well that isolates the active regions as long as the substrate has the lowest potential of the circuit.


(https://www.richis-lab.de/images/Opamp/76x11.jpg)

Looking at the mask of the p-doping just described, we see that this not only creates isolated areas for the active elements. The areas under the bondpads are also isolated from the rest of the circuit. Only the bondpad in the lower right corner is an exception. The negative supply potential is transmitted via this bondpad, which is connected to the substrate.

In the active structures, the n-doping of the wells hardly stands out optically. It can be confined via the surrounding structures. In the next step, the isolation frames are widened. This means that the surroundings of the narrow isolation frames do not yet contain the n-doping. The boundary of the n-doping is the edge surrounding the buried collector. Above the buried collector, of course, there is this n-doping too.

There was a small mistake:
The epi layer is n-doped and the following doping is p and forms the walls of the wells.
Due to hot-linking the pictures above are no correct and the text was modified.  :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on June 22, 2023, 08:01:58 pm
(https://www.richis-lab.de/images/Opamp/77x01.jpg)

Here we have an A109 built in October 1980 (MO), three years later than the previous one.


(https://www.richis-lab.de/images/Opamp/77x02.jpg)

Here the mass joining the two ceramic parts is somewhat irregular like we have seen it with the previous A109.


(https://www.richis-lab.de/images/Opamp/77x04.jpg)

(https://www.richis-lab.de/images/Opamp/77x03.jpg)

Compared to the 1977 A109, a reduction in the outer area reduced the silicon needed from 1,2mm x 1,2mm to 1,0mm x 1,0mm.


(https://www.richis-lab.de/images/Opamp/77x06.jpg)

Functionally, the 1980 A109 has the same structure as the 1977 A109. The auxiliary structures for monitoring the alignment of the masks have been moved to the bondpads in the upper left and lower right corners. The small structure at the bottom edge has been dropped. A test transistor has been added to the top area of the die. To integrate this, a resistor has been relocated a little. In addition, the alternative resistor for setting the bias in the differential amplifier has been omitted. Otherwise, the structures are identical.


(https://www.richis-lab.de/images/Opamp/77x05.jpg)

An irregularity can be found between the input bondpads. It is difficult to say whether this was a weakness in the manufacturing process or whether it is damage caused by an electrical overload.


https://www.richis-lab.de/Opamp73.htm (https://www.richis-lab.de/Opamp73.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: edavid on June 22, 2023, 08:23:42 pm
Here the mass joining the two ceramic parts is somewhat irregular like we have seen it with the previous A109.

FYI, that is called frit.

https://en.wikipedia.org/wiki/Glass_frit_bonding


Title: Re: Opamps - Die pictures
Post by: Noopy on June 22, 2023, 08:33:41 pm
Here the mass joining the two ceramic parts is somewhat irregular like we have seen it with the previous A109.

FYI, that is called frit.

https://en.wikipedia.org/wiki/Glass_frit_bonding

Yeah, this strange glass stuff...  ???
Low temperature melting glass is somehow weird... ;D
Title: Re: Opamps - Die pictures
Post by: Noopy on July 15, 2023, 07:35:25 pm
(https://www.richis-lab.de/images/Opamp/78x01.jpg)

Texas Instruments has a NE5532 in its range, which can be obtained as NE5532, NE5532A, SA5532 and SA5532A. The SA5532s are specified for an increased operating temperature range of -40°C to 85°C. For the A variants, a maximum noise voltage is specified in addition to the typical noise voltage.

The circuit diagram above is from the Texas Instruments datasheet. The functionality of the circuit is described in detail in the Philips NE5532 framework.


(https://www.richis-lab.de/images/Opamp/78x02.jpg)

The areas of the two symmetrically constructed opamps can be clearly seen.


(https://www.richis-lab.de/images/Opamp/78x04.jpg)

The elements of the input amplifier (green) that are sensitive to temperature gradients are arranged in such a way that they are affected as little as possible by the heat dissipated of the output transistors (red).


(https://www.richis-lab.de/images/Opamp/78x03.jpg)

In the middle of the die is the designation 5532B and the year 1999. The B could stand for a second revision of the design.

A large part of the circuit is taken up by the four large capacitors.


https://www.richis-lab.de/Opamp74.htm (https://www.richis-lab.de/Opamp74.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on August 01, 2023, 08:10:18 pm
(https://www.richis-lab.de/images/Opamp/79x01.jpg)

The Ferranti ZN459 is a special, very low noise amplifier. The white noise at higher frequencies is typically only 800pV/√Hz and 1pA/√Hz respectively. At a frequency of 25Hz, 3nV/√Hz is specified. According to the datasheet possible applications include infrared imaging and microphone amplifiers. The cutoff frequency is typically 15MHz.


(https://www.richis-lab.de/images/Opamp/79x02.jpg)

The ZN459 is not a classic differential amplifier. The datasheet contains a block diagram. It shows two amplifier stages. The feedback is integrated in the device. This is emphasized in the datasheet as particularly beneficial if one has to evaluate many channels. A center tap of the feedback resistor is connected to a pin and must be connected externally with a capacitor. A differential input is not available. Besides the signal input, the first amplifier just has a connection for the reference potential of the signal.


(https://www.richis-lab.de/images/Opamp/79x03.jpg)

The datasheet also contains a somewhat more detailed block diagram showing details of the input and output stages. As could already be seen in the first block diagram, the input is not differential. It is just a simple amplifier with one transistor. To minimize noise, the emitter has to be connected to the signal reference. If you want to adjust the gain of the ZN459, you have to insert an emitter resistor. However, this increases the noise of the circuit. The feedback feeds directly into the input.

The current consumption of the ZN459 is typically 2,5mA (at 5V). 0,5mA is the current through the input stage. A not too low current in this path is important to keep the noise level low. At the input, the noise level is especially critical since it still experiences full amplification. Above the input transistor is a transistor that provides a constant collector potential (cascode circuit).

At the output, a class A amplifier stage is implemented, in which a NPN transistor operates against a 0,9mA current sink. The output has its own reference potential to keep the input free of interference.


(https://www.richis-lab.de/images/Opamp/79x04.jpg)

(https://www.richis-lab.de/images/Opamp/79x05.jpg)

Unfortunately, the die was damaged a little. The edge length is 0,8mm. The string 6214-III seems to be an internal project designation. In the upper corners you can see the auxiliary structures of six masks, which among other things make it possible to check the alignment of the masks against each other.


(https://www.richis-lab.de/images/Opamp/79x06.jpg)

A test structure is integrated at the upper edge (pink), representing a transistor. In the lower area and on the right edge, further test structures with smaller testpads are shown (red). On the right are two resistors, most likely made of the base material. On the resistor at the bottom edge, you can see an additional square structure above the resistor strip. This is a pinch resistor, where an n-doped rectangle constricts the p-doped strip, increasing the resistance value. The circuit marked with the X contains a transistor and thus represents an emitter follower.

In the active structures, the large transistor in the left area is particularly noticeable (green). This is not the output transistor (blue), but the input transistor. In addition to the relatively high bias current in the input amplifier, this large active area ensures low noise. Extending from the output to the input are the two 180kΩ resistors, each constructed from six pinch resistors (yellow/orange). The datasheet speaks of a "matching" of the amplification factor. There is no matching to be seen here. Probably one wanted to show that the integration of the resistors is well mastered. The gain is specified with 60dB +/-1dB.

The reference potential at the input is just used for the input amplifier. In addition to the input transistor, the circuit that generates the auxiliary potential for the cascode is connected to this reference too. The reference potential of the output is distributed in a star configuration via four lines. The first line serves just as a shield for the input circuit. The second line supplies the central amplifier block. The third line serves exclusively as reference potential for the output transistor. The fourth line sets the potential around the output bondpad and appears to be used for a current source at the input. This area in the upper left corner is somewhat damaged and correspondingly difficult to read. However, you can see that there is a transistor, not a resistor, in the input amplifier supply.


https://www.richis-lab.de/Opamp75.htm (https://www.richis-lab.de/Opamp75.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on August 04, 2023, 07:38:50 pm
I wasn´t right in every point of the ZN459:


(https://www.richis-lab.de/images/Opamp/79x02.jpg)

The global feedback with the two 180k resistor is not a negative feedback but a positive feedback! I assume that should enlarge the input resistance that in the first place is quite low.

Title: Re: Opamps - Die pictures
Post by: Noopy on September 14, 2023, 08:23:38 pm
(https://www.richis-lab.de/images/Opamp/80x01.jpg)

The LH0033 is a fast voltage follower built by National Semiconductor. The maximum permissible supply voltage is 40V. The maximum allowed output current is +/-250mA. The variant with the index C is the slightly worse bin of the device. The following data applies to the better bin. The JFET input stage allows an input current of 10nA to be maintained over the full operating temperature range. The slew rate is specified by the datasheet as typically 1500V/µs. The bandwidth is specified as 100MHz.

The letters LH indicate that this is a hybrid circuit. The circuit is built on a ceramic substrate and much of it is protected by a ceramic cap. Besides this package, the LH0033 was also available in a relatively large TO-8 package.


(https://www.richis-lab.de/images/Opamp/80x04.jpg)

The datasheet shows the relatively simple, two-stage circuit of the LH0033. Application Note 48 describes the circuit in more detail. In the first stage there is a JFET amplifier with a JFET current sink. Q4 generates a bias current that can be controlled with the help of R2. According to the application note, the current is 10mA. Via D1 and R2 a voltage of about 1,1V is established. A voltage of 1,1V is then also established between Gate and Source of Q1. If the characteristics of D1 and R2 are similar to the characteristics of R1 (including R3) and Q5, then the potential at the input corresponds exactly to the potential at the output. Furthermore, if both JFETs Q4 and Q5 have very similar characteristics, then the offset drift of the circuit is very small.

In the second stage, a push-pull output stage with bipolar transistors ensures that the output current does not stress the JFET amplifier stage. Transistors Q2 and Q3 set a certain quiescent current in the output stage, reducing takeover distortion.

With four supply pins, the LH0033 allows the input stage and the output stage to be supplied separately. Two additional pins allow to influence the bias current of the input stage and thus the offset voltage.


(https://www.richis-lab.de/images/Opamp/80x02.jpg)

(https://www.richis-lab.de/images/Opamp/80x03.jpg)

The circuit is simple. The JFETs Q1 and Q4 in the input stage are placed directly next to each other so that they have as similar temperatures as possible, which ensures a low temperature drift. D1 is relatively far away from Q2, which is not ideal. However, perfect placement of all components is difficult to achieve. Resistors R1 and R2 will have some temperature drift too and are very far apart.

To keep the quiescent current through the output stage as constant as possible, transistors Q2/Q3 have been placed in close proximity to output stage Q5/Q6.

The resistors that had to be tuned are outside the cover. Probably the tuning of the resistors was done after closing the cover.


(https://www.richis-lab.de/images/Opamp/80x05.jpg)

(https://www.richis-lab.de/images/Opamp/80x06.jpg)

(https://www.richis-lab.de/images/Opamp/80x07.jpg)

The naming on the JFETs shows that they are Process 51 JFETs from National Semiconductor. This type is described in more detail in the National Semiconductor FET Databook from 1977. The gate can be contacted on the surface or through the substrate.


(https://www.richis-lab.de/images/Opamp/80x08.jpg)

(https://www.richis-lab.de/images/Opamp/80x09.jpg)

The NPN transistors Q2/Q5 show a typical structure. The metallizations on the base and emitter area allow a contacting on two sides. Both transistors have some discoloration in the emitter area and partly in the base area too.


(https://www.richis-lab.de/images/Opamp/80x10.jpg)

(https://www.richis-lab.de/images/Opamp/80x11.jpg)

The PNP transistors Q6/Q3 have a dirty appearance. It is also noticeable that these transistors were contacted with test needles, which could not be seen on the NPN transistors. There is a metal frame in the outer area, which appears too narrow to be contacted. It is probably a protection of the interfaces in the outer area of the transistor.


(https://www.richis-lab.de/images/Opamp/80x12.jpg)

Diode D1 is another NPN transistor where the base-emitter path is used as a diode. Here, damage is clearly visible in the upper left corner. Presumably, a current flow occurred in reverse direction. Since this is a base-emitter path, the breakdown voltage must be very low. If due to a fault there is a positive potential at pin 7 a high current can flow to the negative supply potential.


https://www.richis-lab.de/Opamp76.htm (https://www.richis-lab.de/Opamp76.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on October 05, 2023, 02:45:22 pm
(https://www.richis-lab.de/images/Opamp/81x01.jpg)

The device you can see here is obviously from Analog Devices and was manufactured in 1984. A research for the designation AD41632 didn´t give any clues which function is hidden behind it. As will be shown, the device is the instrumentation amplifier AD624. Maybe there war a special binning or the module was specially calibrated, so that a different designation was appropriate.


(https://www.richis-lab.de/images/Opamp/81x02.jpg)

(https://www.richis-lab.de/images/Opamp/81x03.jpg)

Several pins are connected to the die with two bondwires. On the right, these are the supply pins. On the left, these are the contacts for setting the amplification factor. The resistance values are very small in this area, so that small changes of the resistances in the bondwires can change the behavior of the circuit. The two parallel bondwires offer lower resistance and thus also lower, absolute temperature drift.


(https://www.richis-lab.de/images/Opamp/81x06.jpg)

The dimensions of the die are 4,3mm x 2,6mm.


(https://www.richis-lab.de/images/Opamp/81x10.jpg)

(https://www.richis-lab.de/images/Opamp/81x11.jpg)

On the die there are the numbers 624, which refer to the AD624. The circit was obviously designed in the USA.


(https://www.richis-lab.de/images/Opamp/81x07.jpg)

The AD624 datasheet Revision C from 1999 contains a picture of the metal layer. The structures differ in some places from the die seen here, which apparently dates back to 1984. The earliest mentioning of the AD624 is in an advertisement in the magazine Computer Design in February 1984. The chip we have here appears to be a very early one. The metal layer from the datasheet contains the year 1991, and this image is not found in older datasheets. This suggests that the design was updated in 1991.

Apart from a few details in the circuit, the first thing you notice is that the die from the datasheet is larger. One has extended the lower edge to integrate a test structure. There are also several letters that could be initials of developers: KH, SW and GM. This is surprising. Non-functional elements often disappear during further development.


(https://www.richis-lab.de/images/Opamp/81x04.jpg)

The datasheet shows a block diagram of the AD624. The instrumentation amplifier consists of the usual configuration of three opamps, with the opamps at the input doubled up. The first amplifier serves mainly as a buffer stage. The second amplifier does most of the voltage amplification.

The AD624 contains resistors that allow various gain factors to be set (1 - 1000). Integration on the die guarantees very similar temperatures, reducing the effects of temperature drift. Since the production includes an adjustment process, the amplification factors can be specified with small tolerances. In the best binning, the deviation from the set amplification is a maximum of 0,25% (G=200, G=500).

Finally, at the output there is an output driver with a feedback and a reference input, so that voltage drops on the line impedances can be compensated.

The AD624 may be operated from +/-6V to +/-18V, typically consuming 3,5mA. The index S binning allows an operating temperature range of -55°C to 125°C. The cutoff frequency is specified as 25MHz. Current noise is 60pA, voltage noise is 0,2µV from a gain of 200 (frequency ranges: 0,1-10Hz).


(https://www.richis-lab.de/images/Opamp/81x23.jpg)

The datasheet shows how very many amplification factors can be set with different interconnections of the integrated resistors without the need for external resistors.


(https://www.richis-lab.de/images/Opamp/81x05.jpg)

Analog Devices has published a more detailed schematic in the document "Linear Design Seminar". At first glance, this looks completely different, but it does not contradict the simpler overview in the datasheet. There are buffer stages (light green) at the inputs. The transistors on each side are doubled, which can be seen here only by the double designation. As will be shown, the transistors are cross-connected. Temperature drifts thus affect the circuit as evenly as possible and influence the signal only very little.

The input resistors and the diodes protect the transistors from too high and too low input voltages by limiting the current flow. Bipolar transistors usually provide better common mode rejection than FETs. This results in a low offset voltage of maximum 75µV. The relatively high base currents are compensated by two current sources (orange), whose currents adapt to the respective operating points. The datasheet specifies a bias current of maximum +/-15nA for the best bin.

The AD624 is based on a concept called "cross degeneration" or "pi degeneration". Each differential amplifier branch has its own current sink (I3, I4, dark green). The resistance between the two branches (cyan) defines the amplification factor. The current sources I1 and I2 (purple) ensure that the outputs of the buffer stages behave like current sources.

Between the input amplifiers are the opamps A1 and A2 (blue, red), which do the voltage amplification. A voltage source is connected to the non-inverting inputs, which is used to set the bias (pink). In parallel to the opamps the capacitors C3 and C4 are integrated, which limit the bandwidth. The outputs of the two amplifiers directly represent the differential output of this stage.

The feedback and therefore the definition of the amplification factor is done by the resistors R56 and R57 in combination with the resistance between RG1 and RG2. The interconnection ensures that the current through the resistor RG is driven by the opamps and does not load the input transistors. In fact, the potentials and currents at the transistors actually remain constant, ensuring very linear behavior.

The four 10kΩ resistors at the output amplifier (yellow) are critical elements. Their resistances have to be as equal as possible in order not to worsen the high common mode rejection of at least 115dB in the best bin (G=500).


(https://www.richis-lab.de/images/Opamp/81x08.jpg)

The individual circuit blocks are easy to identify on the die. The input amplifier is on the left and the output stages are integrated on the right. The output stages have their own supply bondpads, so that the higher currents flowing there influences the remaining circuit parts as little as possible. The four input transistors are arranged in the known cross configuration (light green). The bias current compensation (orange) was integrated in the immediate vicinity.

To the right there are the two current sinks in the emitter paths and the two current sources in the collector paths of the input transistors (dark green/purple). The associated resistors provide the geometries for matching the individual current sinks and current sources, respectively. The pins Output NULL influence the current sinks. Since an offset at this point is multiplied with the amplification factor, the offset voltage at the output can be adjusted with Output NULL. The pins Input NULL adjust the current sources and are used (without amplification) to compensate the offset at the input.

At the upper left edge of the die is the resistor network, which can be used as resistor RG. Between the input transistors and the opamps a buffer stage has been integrated, which is not shown in the datasheet (white). It consists of a pair of transistors and two current sources. To the right, at the upper and lower edge, resistors R56 and R57 follow, which feed the output signal of the opamp A1 and A2 (blue/red) back into the input amplifier. Testpads allow direct adjustment of these resistors.

The opamps A1, A2 and A3 (blue/red/yellow) occupy more than half of the right area. The unmarked circuit parts seem to represent a bias reference. The voltage source defining the potential at the non-inverting inputs of the opamps A1 and A2 is also located in this area (pink). The input transistors of the three opamps are equipped with J-FETs. These are all located with their current sources in the middle of the dies Temperature drifts in the input stages of the opamps A1/A2 are relatively uncritical as long as they occur equally in both opamps. For this reason, the off-center, horizontal placement of the input transistors is not problematic. More important is the symmetrical arrangement of the two input transistor pairs. The remaining circuit parts of the opamps A1/A2 (blue/red) extend to the right edge where the output stages are integrated.

In the case of the opamp A3 (yellow) the temperature drift is more critical. Accordingly, the input transistors have been doubled and sensibly distributed. The adjustment of the input stage is done by two very large resistors, which allow a quite accurate adjustment. The output stage of this opamp is also integrated at the right edge of the die. This arrangement and the symmetry of the complete circuit guarantee low temperature drifts. Resistors R52, R53, R54 and R55, which are particularly critical for common mode rejection, have been integrated on the edges in the right-hand section. Small capacitors are connected in parallel to resistors R53 and R55 to limit the bandwidth of the output amplifier.


[...]

 :-/O
Title: Re: Opamps - Die pictures
Post by: Noopy on October 05, 2023, 02:46:29 pm
(https://www.richis-lab.de/images/Opamp/81x14.jpg)

On the die, a square of the resistor material is integrated, which is used to adjust the laser process. In the upper right corner there is an area engraved with a 3. Perhaps this can be used to trace the alignment process or to record the quality of the alignment.


(https://www.richis-lab.de/images/Opamp/81x12.jpg)

The resistors, which can be used as RG, offer several adjustment possibilities. Thinner elements are cut completely if necessary. A thicker element has just been cut a little. The very wide element perhaps is kept for an adjustment too.


(https://www.richis-lab.de/images/Opamp/81x13.jpg)

The resistors around the opamp A3 have a special shape, which is more often found with adjustable resistors.


(https://www.richis-lab.de/images/Opamp/81x15.jpg)

In the "Linear Design Seminar" Analog Devices describes why the different shapes are chosen. The easiest way is to make a horizontal cut in a simple strip. If you change the direction of the cut during the adjustment, you can adjust the resistance value more precisely. However, both variants lead to high current densities in the remaining resistance area. The third variant does not have this weakness, since the cut is made in a bulge. For this variant, however, the initial resistance value must already be reasonably accurate.


(https://www.richis-lab.de/images/Opamp/81x16.jpg)

The figure above is also taken from the "Linear Design Seminar" by Analog Devices. Besides the AD624 there are two slightly different variants, the AD524 and the AD625. All three devices are still in production, but are marked as NRND ("not recommended for new design"). The AD524 seems to have been the original development. It is already mentioned for the first time in 1982 in the Data Acquisition Databook of Analog Devices. The AD524 has JFETs at the inputs to protect the device from overload. In the AD624, 50Ω resistors replace these JFETs. In addition, the integrated RG resistors have been adjusted somewhat so that several different gain factors can be set. In the AD625 these resistors are missing. They have to be added externally.


(https://www.richis-lab.de/images/Opamp/81x24.jpg)

The datasheet of the AD524 also contains a picture of the metal layer, but the quality is worse. It is nevertheless clear that, apart from the input protection circuitry, the present AD624 is more similar to this design than to the picture in its own datasheet. The year 1987 can be seen in the right area.


(https://www.richis-lab.de/images/Opamp/81x17.jpg)

A closer look at the metal layer shown in the AD624 datasheet reveals that the input transistors are contacted differently. In the AD624 we have here, each of the four input transistors has two emitters. The illustration in the datasheet clearly shows that there is only one emitter contact. This means that during development the input transistors were changed from two emitters to one emitter. In the datasheet of the AD524, due to the more complex metal layer in the area of the input transistors, it can be assumed that transistors with two emitters were used here too. That fits with the chronological sorting.


(https://www.richis-lab.de/images/Opamp/81x18.jpg)

Another difference in the metal layer can be seen in the area of the bondpads Output NULL. This is the offset adjustment that still passes through the amplification of the device. The newer metal layer in the datasheet obviously contacts two resistors directly at the bondpads. The size of the area suggests that the resistors could be aligned. The initial offset adjustment itself is already done at the corresponding current sinks. This means that it was considered necessary to additionally adjust the path for the external adjustment. Of course it is possible to react to different tolerance levels with an external adjustment, but the behavior is less predictable. With the addition of the adjustable resistors, the two resistors down the line have been shorted.


(https://www.richis-lab.de/images/Opamp/81x09.jpg)

On the die, in addition to NPN and PNP transistors, there are also p-channel JFETs. However, special interest is aroused by unusual structures, which obviously consist of two elements.


(https://www.richis-lab.de/images/Opamp/81x21.jpg)

(https://www.richis-lab.de/images/Opamp/81x19.jpg)

(https://www.richis-lab.de/images/Opamp/81x20.jpg)

These unusual elements are combinations of PNP transistors and p-channel JFETs. The structures of the PNP transistor are somewhat self-explanatory. The emitter is a p-doped circle located in an n-doped area, which is the base. An outer p-doped ring forms the collector. The base surface is contacted with a strong n-doping.

The p-doped collector ring extends to the right to the first source contact of the JFET. In fact, this p-layer extends over the complete area of the JFET and is alternately contacted as source and drain. Above this is an n-doped layer, which is the gate. Below the p-doped source-drain layer, the silicon is also n-doped.

The red appearing stripes above and below the JFET cannot be assigned immediately. The color would speak for a p-doping, which, however, would not make sense. The colors just result from the different thicknesses of the silicon oxide layers, they do not say anything about the doping by themselves. It seems most likely that we see the heavy n-doping that serves as base and gate feed line across the entire device. The different color probably results from an additional or differently shaped layer that is just in the area of the JFET. Probably that is a special thing of the process.

In common bipolar processes, n-channel JFETs are often used as simple current sources. Integrating rudimentary JFET structures is relatively easy. However, it is much more complicated to build JFETs whose quality is sufficient for high-quality analog signal processing. Consequently, it may well be that the above JFET structures were made using a special process. Apparently, the properties of the JFETs were sufficiently important to the AD624 to justify the extra effort.


(https://www.richis-lab.de/images/Opamp/81x22.jpg)

The double structures are used as current sources in the AD624. Apparently, these double structures have particularly advantageous properties.


https://www.richis-lab.de/Opamp77.htm (https://www.richis-lab.de/Opamp77.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on October 05, 2023, 08:40:29 pm
These PNP+JFET hybrids are kind of cascodes. They don't quite eliminate Miller effect because gates are connected to the input signal instead of ground, but they improve output impedance of those lateral PNPs. It looks like there is more JFETs on this chip.

The input stage is typical for monolithic instrumentation amps. Q1,I1,A1 and Q2,I2,A2 can be regarded as a pair of two-stage opamps with single transistor input stages, together realizing the usual instrumentation amp topology. The simple input stages have -0.7V offset voltage, but it's matched between opamps and cancels out differentially, and lower noise than ordinary differential pair input stages consuming same bias current and die area. They also realize current feedback, which helps maintain consistent bandwidth over a very wide range of closed loop gains.
Title: Re: Opamps - Die pictures
Post by: David Hess on October 06, 2023, 12:14:08 am
The simple input stages have -0.7V offset voltage, but it's matched between opamps and cancels out differentially, and lower noise than ordinary differential pair input stages consuming same bias current and die area. They also realize current feedback, which helps maintain consistent bandwidth over a very wide range of closed loop gains.

More details of this type of instrumentation amplifier are available in application notes for dual and quad monolithic matched transistors like the LM395 and MAT series.
Title: Re: Opamps - Die pictures
Post by: Noopy on October 06, 2023, 03:06:17 am
These PNP+JFET hybrids are kind of cascodes. They don't quite eliminate Miller effect because gates are connected to the input signal instead of ground, but they improve output impedance of those lateral PNPs. It looks like there is more JFETs on this chip.

Sounds reasonable...  :-+
Yes, there are more JFETs. The input stages of the opamps A1 and A2 use JFETs.


The input stage [...] lower noise than ordinary differential pair input stages consuming same bias current and die area.

Why is that? Because you just have one branch and not the typical the second branch of a differential amplifier?


They also realize current feedback, which helps maintain consistent bandwidth over a very wide range of closed loop gains.

And the input stage doesn´t have to supply the RG current.  :-+


More details of this type of instrumentation amplifier are available in application notes for dual and quad monolithic matched transistors like the LM395 and MAT series.

I will take a look!  :-+
Title: Re: Opamps - Die pictures
Post by: magic on October 06, 2023, 05:12:28 am
The input stage [...] lower noise than ordinary differential pair input stages consuming same bias current and die area.
Why is that? Because you just have one branch and not the typical the second branch of a differential amplifier?
If the input stage is one transistor with the base being IN+ and the emitter being IN-, equivalent voltage noise is simply the voltage noise of this transistor.

If the input stage is a differential pair with emitters together and the bases being IN+ and IN-, equivalent voltage noise is the sum of the noise from both transistors. This is 3dB  higher if both transistors are identical, while power consumption and die area are doubled. If bias and dimensions are reduced 50% to match the single transistor stage, noise increases further to 6dB over single transistor.

I think main reason we don't see such input stages in normal opamps is the slightly inconvenient 0.7V offset voltage ;)
This, and IN- also becomes low impedance, but many applications can tolerate current feedback just fine.

In early days of transistors, such input stages were used in many audio amplifiers. Saved one transistor. AC coupling or trimming pots eliminated the offset voltage.
Title: Re: Opamps - Die pictures
Post by: Noopy on October 06, 2023, 05:37:12 pm
Thanks for your explanation! That was my what I had in mind. :-+
Title: Re: Opamps - Die pictures
Post by: magic on October 17, 2023, 04:35:42 pm
Texas Instruments OP07

Quote
Obsolete and no longer available from Texas Instruments.

SNOA471B (http://www.ti.com/lit/an/snoa471b/snoa471b.pdf), page 38


A fairly inexpensive basic grade OP07 is available from Texas Instruments. The chip appears to follow the PMI original (https://www.eevblog.com/forum/projects/opamps-die-pictures/msg4398712/#msg4398712) in circuit topology and layout quite exactly. A notable difference is proportionally more area eaten up by capacitors; I'm not sure what's going on here. Die size is about 2.25×1.7mm.

From left to right, we see:
- input stage collector load resistors, connected to VCC+ through an additional network of resistors with zener zaps
- the input stage differential pair in standard common centroid layout, bias cancellation injection mirrors north-east and south
- the input stage two level cascode, with the same twisted connection pattern as seen in PMI
- NPN emitter followers driving the second stage
- second stage PNP differential pair, combined with NPN active loads for the drivers (PNP base = NPN collector)
- a long main bias startup resistor and some more resistors
- second stage current mirror
- PNP current mirror biasing the 2nd and 3rd stage
- the third stage
- the output stage
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=244205.0;attach=1903698;image)

This is corrected and cleaned up for readability schematic from old TI datasheets, believed to be complete and accurate at the time of posting ;)
Current datasheet contains μA741 schematic, don't ask :wtf:
(https://www.eevblog.com/forum/index.php?action=dlattach;topic=244205.0;attach=1903704;image)

The weird flat depressions which are not-quite-exactly-aligned with active areas of transistors are the buried layer pattern appearing on the surface of the epitaxial layer. During epitaxial growth, this pattern of depressions shifts sideways (here: north) by approximately the thickness of the epitaxial layer (here: some 17μ). The actual diffusion is still not shifted and remains under the active areas. PMI, Analog and Linear developed processes where this shift doesn't occur and edges of the pattern don't cross active areas of transistors.

Buried layer is absent under the output PNP emitter follower (second structure north of VCC- pad). This is because it's a substrate PNP and buried layer would increase recombination of injected holes headed towards the substrate collector and thus decrease β. Instead, low resistance base connection is provided in the form of N+ diffusion on the surface. Buried layer is also absent under capacitors, except for one, perhaps for the junction capacitance which it represents between VCC+ and VCC-, but I don't really know.


A higher resolution version of the image is attached below, scaled to approximately 1μ per pixel. This image was also a test whether a 5x microscope objective has enough resolution to capture important details of "easy" bipolar ICs that don't have very dense structures. Some contact windows aren't fully resolved from metal edges, not a major problem. More importantly, emitters, PNP collectors and such are mostly visible when they extend beyond the metal contacting them, which saves a lot of guesswork. So the answer is "it can work", but this chip is quite nondemanding on the optics...

The die is in slightly less than perfect condition because it served as a test subject for quite some time, but I don't feel like decapping another one.
Title: Re: Opamps - Die pictures
Post by: Noopy on October 17, 2023, 04:58:33 pm
A notable difference is proportionally more area eaten up by capacitors; I'm not sure what's going on here.

Perhaps a more modern process with higher gain-bandwidth-product and because of this you need more compensation?


Current datasheet contains μA741 schematic, don't ask :wtf:
:-DD


This image was also a test whether a 5x microscope objective has enough resolution to capture important details of "easy" bipolar ICs that don't have very dense structures.
:-+
Title: Re: Opamps - Die pictures
Post by: AnalogTodd on October 17, 2023, 06:20:00 pm
The weird flat depressions which are not-quite-exactly-aligned with active areas of transistors are the buried layer pattern appearing on the surface of the epitaxial layer. During epitaxial growth, this pattern of depressions shifts sideways (here: north) by approximately the thickness of the epitaxial layer (here: some 17μ). The actual diffusion is still not shifted and remains under the active areas. PMI, Analog and Linear developed processes where this shift doesn't occur and edges of the pattern don't cross active areas of transistors.
The buried layer shift comes based on the crystal structure used in the wafer and subsequently causes the shadow of its location to shift as the epitaxial layer is grown. Depending on whether or not you are using a 100, 110, or 111 wafer will determine if you get a shift or not. One interesting bit is that the wafer supplier has to saw the flat edge of a wafer in a specific location based on the structure used or you won't know what direction the shift will occur in when you grow the epi. This is a problem because you are aligning to what you see for the buried layer after the epi is grown, and if it is in a different location than expected, your isolation can cross over the buried layer and won't actually isolate anything. I have seen this occur once before where a run of wafers came out of fab and the flat was sawn on the wrong side of the wafer and all the tubs were shorted to each other.
A notable difference is proportionally more area eaten up by capacitors; I'm not sure what's going on here.
Perhaps a more modern process with higher gain-bandwidth-product and because of this you need more compensation?
More than likely a different process overall where the amount of capacitance per unit area is a lot lower. Depending on the process, one manufacturer may be able to get away with capacitors formed by reverse-biased junctions, whereas these capacitors are metal-oxide-silicon (MOS) devices. Even if both used the same MOS capacitor, the thickness of the oxide layer is a main factor in capacitance per unit area (maybe one process has an option for stripping the oxide in the capacitor region and regrowing a thinner oxide, I've used that before in bipolar processes and it's common with gate oxides in CMOS devices). The capacitance needed is going to be based more on the circuit biasing than the transistor bandwidth, and a big bipolar process like this is going to be notoriously slow, especially with lateral PNP devices.
Title: Re: Opamps - Die pictures
Post by: magic on October 17, 2023, 06:58:22 pm
Depending on whether or not you are using a 100, 110, or 111 wafer will determine if you get a shift or not.
So what would be the advantage of such wafers? They seem to be widely used on jellybean bipolar ICs, despite making mask alignment harder for the fab.

OTOH, the likes of PMI/AD/LT clearly avoided them, I noticed it a while ago.
Title: Re: Opamps - Die pictures
Post by: magic on October 17, 2023, 11:14:42 pm
National Semiconductor LM4562

Quote
No details of the internal circuitry have been released so far, and quite probably never will be.

Douglas Self (https://www.eetimes.com/op-amps-in-small-signal-audio-design-part-3-selecting-the-right-op-amp/)

LM4562 is a high performance bipolar opamp designed by National Semiconductor primarily for audio applications, featuring quite high speed, low distortion, better than average load driving ability, low broadband voltage noise, but somewhat more current noise than the popular NE5532. It looked like a serious effort at attacking the established position of NE5532, with better performance in almost every regard, probably the most audio specs in any datasheet at the time, and some marketing effort. National released it in metal cans to cater to audiophiles, and Bob Pease himself swore that it sounds good. While not as cheap as jellybean opamps, not horrendously expensive either, unlike some other "better than 5532" options out there.

Widely believed (but I haven't verified) to be the same part as LME49720, which started a whole series of LME opamps, power amplifier drivers and similar audio ICs, before TI took over and discontinued most of them. LM4562 was also meant to get axed, but there was apparently a sizable and vocal enough user base for the bean counters to reconsider.

The inside reveals a modern complementary bipolar process with no lateral PNPs in sight and higher density compared to jellybean chips. This die is actually smaller than OP07 at roughly 1.8×1.5mm, but it packs two channels and probably more transistors than OP07 in each of them. There is one layer of metal interconnect and a layer of what I suppose is polysilicon, used for resistors, lower plates of capacitors and to cross traces. Immediately visible are substantial output stages in diamond buffer topology and several caps. The input stages use common centroid layout, with no additional means of offset voltage control like fuses or laser trimming, typical for an audio-oriented chip. Worst case offset is 0.7mV.

Long resistors at the bottom power the main bias generators, as per US3930172.

(https://www.eevblog.com/forum/index.php?action=dlattach;topic=244205.0;attach=1903902;image)

A closer look at individual transistors reveals two types: with and without frames ;D By tracing connections with supply rails it becomes evident that the "framed" transistors are PNP and the "unframed" are NPN - same as in TP1322 / HA-2520. In each case the active area is the emitter strip in the center and the base is connected from both sides. Isolation between transistors is not visible. The transistors below are the input stage, by the way, and we can answer Douglas Self's doubts: yes, there is bias cancellation, the small NPNs at the bottom are a current mirror sinking from the input pins. The differential pair is PNP with no emitter degenation and no cascoding, collectors go to a current mirror at the negative rail. This looks like a two stage topology.

(https://www.eevblog.com/forum/index.php?action=dlattach;topic=244205.0;attach=1903908;image)


Higher resolution image at 400nm/px below.
Title: Re: Opamps - Die pictures
Post by: AnalogTodd on October 18, 2023, 01:58:50 pm
Depending on whether or not you are using a 100, 110, or 111 wafer will determine if you get a shift or not.
So what would be the advantage of such wafers? They seem to be widely used on jellybean bipolar ICs, despite making mask alignment harder for the fab.

OTOH, the likes of PMI/AD/LT clearly avoided them, I noticed it a while ago.
Oh man, it's been 30+ years since I did my materials science class going over this...I'll try to remember what I can. I'm not a process engineer, but instead an IC design engineer so my understanding isn't as deep as some. I know about LTC moving away from the wafers with the buried layer shift, I was a designer there from the mid-90's until a few years after the acquisition by ADI.

Mask alignment really isn't harder for the fab, they are aligning to the visible buried layer whether there is a shift or not. Where it gives concerns is the visible buried layer, while not physically located where seen, has damage in the lattice that you don't want going through sensitive circuitry, so you'll see things like bandgap transistors oriented to avoid that from going through the critical junctions (NPN emitters are a big one).

The different wafer types define how the face of the wafer is cut relative to the crystal structure. The diamond structure of silicon means you can cut in one of three ways:(https://i.stack.imgur.com/lhWUp.png)
Each of these gives different characteristics in different places. Etching definitely changes as a function of crystal structure. Oxide growth and reliability is affected by this, as is the number of dangling bonds that occur at the surface (since the surface atoms will be missing connections that would normally exist). One concern with dangling bonds is hydrogen getting in, it readily gets through silicon dioxide (but not through plasma enhanced nitride) and the hydrogen readily latches onto those dangling bonds. This causes issues with changes in the charge right at the surface of the silicon and causes huge shifts in device parameters.

Honestly, I think a lot of the reason for using different wafer crystal structures over the years has been a matter of overall manufacturability and reliability that was attainable at the time. As technology and understanding has moved forward, there has been a move to the different crystal orientations for newer processes. Of course, the older products are not going to be redesigned into the new processes because the time required to do so is expensive compared to just continuing to manufacture on the existing process. Almost all of the older processes can still be manufactured on newer tools, so fabs don't need to keep decades old equipment up and running. Personally, I feel that there is a loss in the industry right now of knowledge of these older processes and the pros and cons of them as new people coming into the business haven't learned about things like these and can't debug problems in these chips. Heck, I've interviewed some new grads that have no clue about how to use bipolar devices because schools are shifting away from teaching it.
Title: Re: Opamps - Die pictures
Post by: Noopy on October 24, 2023, 03:06:09 am
(https://www.richis-lab.de/images/Opamp/82x01.jpg)

Here you can see a relatively new µA709 from Fairchild. Fairchild sold the µA709 for the first time in 1965.


(https://www.richis-lab.de/images/Opamp/82x02.jpg)

(https://www.richis-lab.de/images/Opamp/82x03.jpg)

The dimensions of the die are 1,1mm x 1,0mm. In any case, this is not the first revision of the design. On various websites there are pictures of the first µA709, which have a slightly different design. There are seven mask revisions on the die. 7709N could be an internal designation.


https://www.richis-lab.de/Opamp78.htm (https://www.richis-lab.de/Opamp78.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: RoGeorge on October 24, 2023, 06:08:20 am
I wonder why they didn't rotate the die a little counterclockwise, so to minimize the length of the bonding wires?
Title: Re: Opamps - Die pictures
Post by: iMo on October 24, 2023, 07:02:17 am
Long time back (say till 90ties) the bonding was done manually (a large room full of young ladies staring into their microscopes, they worked in 1-2hours shifts not to lose their eyesight..).
Thus they did regardless how the die happened to be positioned.

PS: also they soldered or glued the die into the package manually as well..
Title: Re: Opamps - Die pictures
Post by: Gyro on October 24, 2023, 09:30:52 am
The bond wires all look to be roughly equal and generous lengths. Maybe they had difficulties with short wires, excessive flexing of the first bond while running out to the second one? Keeping them relatively horizontal rather than significantly domed might have been a limitation of the early ultrasonic bonding heads. Maybe less vertical travel or visual depth of field? I bet there was probably some subtle reason why longer bond wires were 'easier'.
Title: Re: Opamps - Die pictures
Post by: exe on October 25, 2023, 09:34:21 am
Widely believed (but I haven't verified) to be the same part as LME49720, which started a whole series of LME opamps, power amplifier drivers and similar audio ICs, before TI took over and discontinued most of them. LM4562 was also meant to get axed, but there was apparently a sizable and vocal enough user base for the bean counters to reconsider.

LME49720 is my current favourite bipolar opamp. It is fast, wide phase margin, and, what surprised me, has very low (for an opamp) open loop output impedance of 13 Ohm. That's by far lower than most of other opamps in its category. Looking at LM4562 datasheet, it also specifies the same output impedance. I don't think it's a coincidence.
Title: Re: Opamps - Die pictures
Post by: magic on October 25, 2023, 10:46:46 am
Emitter followers work like that; none of that rail to rail rubbish :D
Did you try NE5534/2? I think it could be fairly low as well, though maybe not 13Ω but closer to 15~20Ω.
Title: Re: Opamps - Die pictures
Post by: exe on October 25, 2023, 11:34:21 am
Emitter followers work like that; none of that rail to rail rubbish :D
Did you try NE5534/2? I think it could be fairly low as well, though maybe not 13Ω but closer to 15~20Ω.

Hmm, interesting, I googled it and I found that indeed most NE5532 have output impedance of around 20-30 Ohms ([1], though there is one outlier from HGSEMI with impedance of 149  :--). That surprises me, as I thought there should be emitter resistors to protect output stage.
I think my confusion comes from the plot in AoE 3 (page 311) (attached). Most opamps don't come even close to the LME49710. However, most opamps there are not audio opamps. I think some audio opamps are designed to have lower output impedance so that they can drive heavier loads with less distortion.

Well, I'm even more proud of NE5532, though still like my LME49720 due to lower input bias).

[1] https://s-audio.systems/blog/5534-measurement/?lang=en
Title: Re: Opamps - Die pictures
Post by: magic on October 25, 2023, 12:23:10 pm
TI and Raytheon specify 14~15Ω per resistor and they are effectively in parallel, but also in series with output resistance of emitter followers at maybe ~2mA bias.
LM4562 is a bit of power hog, it helps if significant current flows in the output stage.

outlier from HGSEMI with impedance of 149
Chinese manufacturer, datasheet stolen from TI with replaced logo and some pages missing. I'm sure it's legit ;D

And what's that, 30° phase margin in their internally compensated dual? :wtf:
Title: Re: Opamps - Die pictures
Post by: magic on October 29, 2023, 03:29:24 pm
Japan Radio Company NJM2068
Quote
The NJM2068 is a high performance, low noise dual operational amplifier. This amplifier features popular pin-out, superior noise performance, and superior total harmonic distortion.

An older Japanese Hi-Fi opamp, not as good as NE5532 but performs relatively well at low gain with light loading. In recent years the chip has gained some Internet fame thanks to its use in headphone amplifiers like Objective2 and JDS Atom. Typically for Japanese opamps, exact input noise density specifications appear to be a secret of the manufacturer, but I can reveal that broadband noise voltage is ~3.5nV/rtHz.

The datasheet schematic shows 4558 topology. Compensation is somewhat more complex than usual and the chip exhibits typical for audio opamps high open loop gain at low frequencies, followed by fast falloff below 1MHz and unity gain crossover at a few MHz. Old age and differential input voltage rating of ±30V suggest lateral PNP input stage, making NJM2068 possibly the highest performance opamp with such inputs ever made.

(https://www.eevblog.com/forum/index.php?action=dlattach;topic=244205.0;attach=1914495;image)

The inside looks typical for a 4558 style amplifier. Output transistors of each channel are laid out in line with the corresponding input stage like in precision opamps, but input stage common centroid layout is not used.

(https://www.eevblog.com/forum/index.php?action=dlattach;topic=244205.0;attach=1914483;image)

Input transistors are made of eight paralleled lateral PNPs each. The darker rounded rectangles with holes are collectors and the small circles are emitters, both embedded in a larger N-doped region which is the base. Active base region where transistor action happens is the gaps between emitters and collectors. Base potential is distributed around the area by a surface N+ diffusion and additional metal strips on the sides of the collectors. Buried N+ diffusion is also employed below the PNP structure (and elsewhere), but poorly visible on this image. Buried layer pattern shift is present in this process.

An unusual feature, indicated with arrows below, are thin "frames" surrounding all contact windows and typically, but not always, extending in the direction where the metal trace is coming from. I have absolutely no idea what they are.

I expected to maybe see evidence of additional doping applied to PNP emitters. There clearly is "something" there, as pointed by one of the arrows, but it could be the same contact window thing as elsewhere. No idea what's going on :-//

(https://www.eevblog.com/forum/index.php?action=dlattach;topic=244205.0;attach=1914570;image)

Attached below full chip at 400nm/px. This and LM4562 were both shot with a 10x0.25 microscope objective, which appears to be about good enough for 40V bipolar technology.
Title: Re: Opamps - Die pictures
Post by: AnalogTodd on October 30, 2023, 01:33:31 pm
An unusual feature, indicated with arrows below, are thin "frames" surrounding all contact windows and typically, but not always, extending in the direction where the metal trace is coming from. I have absolutely no idea what they are.

I expected to maybe see evidence of additional doping applied to PNP emitters. There clearly is "something" there, as pointed by one of the arrows, but it could be the same contact window thing as elsewhere. No idea what's going on :-//
What it might be is a mask that is used to create capacitors. The capacitor across the resistor at the bottom of the input stage is N+ to substrate, no surprise as it will likely on see a tiny voltage. However, the cap that goes from the output of that differential pair to the PNP driving the output can see enough voltage to break down a junction capacitor and must be created using an oxide. That oxide must be thick enough to handle a fairly high voltage and may be done by stripping the oxide in the capacitor area and growing a clean and better controlled thickness oxide in the region. Doing this allows for much cheaper steps earlier in the process at the expense of an added mask and step for the capacitor. The issue would be that when contact etching is done you could over-etch enough that you might compromise the capacitor, so to make it simple you just do a logical OR of all contacts and the capacitor to make sure oxides are all the same thickness and the concerns of over-etch go away.

As for the additional doping to the PNP's, that's really not a good idea on an older bipolar process like this. Misalignment of masks could give you one direction where the breakdown is lower than the other as distances between collector and emitter change. You really want those to be the same masking and diffusion so they self-align. You can see evidence of mask misalignment when you look at the NPN emitters in your zoomed in picture--the metal on the left side looks coincident with the contact edge, ideally there would be better coverage (look at top and bottom edges of those emitters).

What I am finding interesting is the use of overlaying the base on the isolation around the die. You can see it done to create the FET just below the V+ pad with the narrow channel through the iso, and in places where contact to the substrate is needed (around the vertical PNP output device is good spot as is the stripe above the V- pad). Down around the input amplifiers it gets used quite a bit but is never contacted. I don't think it is for field relief to help control breakdown voltages, it might just be to get a lower overall resistance to the substrate in case devices saturate, it's hard to tell.

One last interesting item to note is the resistor in series with the emitter of the NPN hanging on the differential amplifier output. It's a small resistor (just above the emitter resistors from the differential pair NPNs) and it has a chunk of N+ over the top of it. This is a pinch resistor where the N+ changes the dopant concentration to make a base diffusion resistor value much higher, (10-100X higher) and the value of the resistor will go up and down proportionally as the NPN beta in the process varies. Seems like it would up the gain of the amplifier quite a bit as process varied, but I don't know well enough to make that call.
Title: Re: Opamps - Die pictures
Post by: Noopy on November 29, 2023, 08:33:01 pm
(https://www.richis-lab.de/images/Opamp/83x01.jpg)

The Fairchild µA776 is an opamp with a very special feature. You can set the bias current of the circuit externally. The supply voltage can be chosen between +/-1,2V and +/-18V. Depending on the bias current at +/-15V the µA776 typically consumes 20µA to 160µA. A high bias current increases the slewrate from 0,1V/µs to 0,8V/µs but also the input bias current from 2nA to 15nA. The datasheet states an overshoot of 10% with the high bias current that doesn´t occur with the low bias current setting. The variant with the index C is specified for an temperature range between 0°C and 70°C. With an index M the temperature range is -55°C to 125°C.


(https://www.richis-lab.de/images/Opamp/83x02.jpg)

The schematic in the datasheet shows a common circuit. The bias currents of the different amplifier sections are generated with some current mirrors (blue). The reference current for the bias circuit is the current flowing out of the Iset pin.


(https://www.richis-lab.de/images/Opamp/83x03.jpg)

The pin carrying the negative supply is connected directly to the package.


(https://www.richis-lab.de/images/Opamp/83x04.jpg)

(https://www.richis-lab.de/images/Opamp/83x05.jpg)

The size of the die is 1,6mm x 1,4mm. The circuit looks like the schematic in the datasheet. In the middle of the die you can see the symmetrical input amplifier section.


https://www.richis-lab.de/Opamp79.htm (https://www.richis-lab.de/Opamp79.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on November 29, 2023, 08:54:25 pm
The circuit looks like the schematic in the datasheet. In the middle of the die you can see the symmetrical input amplifier section.
Almost like the schematic ;)
Note emitter degeneration in the input stage.
Or Q10 overcurrent protection which blows up Q9 when activated (in reality it looks like μA741 protection)

So far I'm not sure if we have ever seen one accurate schematic of any linear IC from Fairchild...

edit: 702 and 709 were OK
Title: Re: Opamps - Die pictures
Post by: Noopy on November 29, 2023, 09:19:25 pm
Let's say it's more correct than most of the μA741 schematics we have seen so far.  :D
Title: Re: Opamps - Die pictures
Post by: Noopy on December 03, 2023, 07:28:44 pm
(https://www.richis-lab.de/images/Opamp/84x01.jpg)

The Teledyne Philbrick TP1321 is an opamp with a high bandwidth and a high input resistance. The amplification factor must not be less than 3. The bandwidth is then at least 33MHz. The input current at room temperature is specified with a maximum of 25nA, the input resistance with 300MΩ.

Like the TP1322 (https://www.richis-lab.de/Opamp49.htm (https://www.richis-lab.de/Opamp49.htm)), the TP1321 belongs to the "optimized 741's" series. Both opamps share the same datasheet. The TP1322 has a higher slew rate, while the TP1321 is specified with a higher bandwidth. The TP1321 is therefore suitable for lower output levels. The Teledyne Philbrick catalog from 1972 states a price of 15$. Today (2023) this corresponds to a value of 112$.


(https://www.richis-lab.de/images/Opamp/84x02.jpg)

(https://www.richis-lab.de/images/Opamp/84x03.jpg)

Although there are only three years between the production of the TP1321 and the TP1322, the assembly technology is clearly different.


(https://www.richis-lab.de/images/Opamp/84x07.jpg)

The wafer was obviously cut a little and then broken at these cut edges.


(https://www.richis-lab.de/images/Opamp/84x04.jpg)

(https://www.richis-lab.de/images/Opamp/84x05.jpg)

(https://www.richis-lab.de/images/Opamp/84x06.jpg)

The dimensions of the die are 1,8mm x 1,3mm. Although the characteristics of the TP1321 and TP1322 are very similar, they are obviously two very different designs. However, the same process from Harris Semiconductor was apparently used, which produces very thin frame structures around the transistors and is described in more detail with the TP1322. For the TP1322 an identical Harris opamp can be found. Harris also specifies alternatives for the TP1321, but these have a different layout.

A relatively large capacitor is integrated at the top left, but it lacks the metal layer that would represent the second electrode. It is quite possible that this design with slightly more compensation was sold with a lower bandwidth.


https://www.richis-lab.de/Opamp80.htm (https://www.richis-lab.de/Opamp80.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: magic on December 04, 2023, 12:01:10 am
The closest Harris part appears to be HA-2622.
The weird circuitry around the input stage seems to match, whatever it is. An attempt at bias cancellation by combining PNP and NPN? :-//

edit
Of course. Q30 and Q31 base currents are equal, so Q29 should approximately cancel Q28.

I tried replacing the schematic with a higher quality version from 1996, but it had errors so back to 1975 we go :palm:
Title: Re: Opamps - Die pictures
Post by: Noopy on December 04, 2023, 04:02:06 am
The closest Harris part appears to be HA-2622.

But just the circuit is similar, the design is a different one (or older or newer).


The weird circuitry around the input stage seems to match, whatever it is. An attempt at bias cancellation by combining PNP and NPN? :-//

edit
Of course. Q30 and Q31 base currents are equal, so Q29 should approximately cancel Q28.

Yes, that´s really interesting!  :-+
Title: Re: Opamps - Die pictures
Post by: Noopy on January 05, 2024, 04:27:28 am
(https://www.richis-lab.de/images/Opamp/85x01.jpg)

With the CA3020, RCA sold a small power opamp, which was available in two versions. The index A marks the better version, whose output stage can be supplied with up to 12V instead of 9V and can conduct at least 180mA continuously instead of 140mA. This increases the output power from up to 0,5W to a maximum of 1W (10% THD). The bandwidth is typically 8MHz. The permissible operating temperature range is specified as -55°C to 125°C.


(https://www.richis-lab.de/images/Opamp/85x06.jpg)

It seems like the A variant has not been sold initially. In this ad in the magazine Electronics from May 1967, there is at least no reference to the A variant.


(https://www.richis-lab.de/images/Opamp/85x07.jpg)

A year later, RCA was already advertising the A version.


(https://www.richis-lab.de/images/Opamp/85x05.jpg)

Today you can often find the Intersil datasheet for the CA3020. Minor errors have crept in there. Two connections have been omitted and resistor R7 is labelled R5. In the datasheet revision from the year 2000, after 33 years of production, the CA3020 is marked as obsolete.

The transistors Q2 and Q3 form a differential amplifier. Transistor Q1 can be used as an upstream buffer stage. The diode chain D1, D2, D3 is used to set the operating point. The voltage from two pn junctions is fed to the inputs of the differential amplifier via R4/R6. The further resistors divide the voltage of the two diodes by slightly more than half. Overall, this generates a certain bias current that is relatively temperature-stable. The potential of the three p-n junctions is applied to the collector resistors R1/R3. While pin 9 is used to supply the circuit, the series resistance of the differential amplifier can be set via pins 8 and 11. A higher resistance reduces the current consumption, but also the output power.

Transistors Q4 and Q5 are driver transistors, from which feedback is fed to the differential amplifier via resistors R5 and R7. The control voltage for the output stage transistors Q6 and Q7 drops out at the emitter resistors R8 and R9. The collector and emitter connections of the output stage transistors are conntected to the pins. One application is driving a load or a transformer with centre tapping. The CA3020 usually works as a class B amplifier. However, it can also be used as a class A amplifier if the potential at the input is raised accordingly.

The resistors in the branches of the differential amplifier are unbalanced in relation to the individual values. This can only be seen here for resistors R5 and R7. The older schematics also note the asymmetry at resistors R1/R3 and R4/R6. However, this also shows that the ratios of the resistors on both sides are not fundamentally different. Why the circuit was not designed completely symmetrical remains an open question.


(https://www.richis-lab.de/images/Opamp/85x02.jpg)

The housing is connected to the reference potential.


(https://www.richis-lab.de/images/Opamp/85x03.jpg)

(https://www.richis-lab.de/images/Opamp/85x04.jpg)

The dimensions of the die are 1,5mm x 1,4mm. 6059 is a typical project designation for RCA. The crosses in the right-hand area are used to check the alignment of the masks to each other.


(https://www.richis-lab.de/images/Opamp/85x08.jpg)

The circuit on the die corresponds to the illustration in the datasheet. Some resistors are constructed in such a way that their contact areas and thus their resistance values can be adjusted more easily. The asymmetry in the differential branches is confirmed.


(https://www.richis-lab.de/images/Opamp/85x09.jpg)

The two large output transistors are located on the right-hand side of the circuit. Each transistor consists of eight small transistors that are directly connected to each other. While the CA3020 is specified for a blocking voltage up to 18V, the CA3020A guarantees a blocking voltage of 25V.


(https://www.richis-lab.de/images/Opamp/85x10.jpg)

Normally one would assume that the A variant is generated by binning the CA3020. However, this may have been different, at least for the first CA3020 parts. The layout of the CA3020 is illustrated in the magazine Electronics in August 1967. There the project designation is 5220 and the output stage transistors each contain just six individual transistors. The remaining geometries are slightly different, but the circuit is the same.

The different layouts and the fact that the A variant is not mentioned in the first adverts suggest that initially only the lower output power was planned and the circuit was expanded later. Perhaps the power was not sufficient for the planned applications or the designers were initially unsure whether the current distribution would still be sufficiently symmetrical with eight transistors. Perhaps the process has also improved.


https://www.richis-lab.de/Opamp81.htm (https://www.richis-lab.de/Opamp81.htm)

 :-/O
Title: Re: Opamps - Die pictures
Post by: RoGeorge on January 05, 2024, 08:09:31 am
Under Fig.1, the text says R values may be +/-30%.

Asking because 30% seems very big to me, when compared to discrete R.  For discrete resistors the largest tolerance I've seen in practice was E6 (+/-20%), and that was decades ago in some tubes circuits.  Wikipedia lists an E3, too, with +/-40%, but I don't recall ever seeing a resistor with +/-40%.  https://en.wikipedia.org/wiki/E_series_of_preferred_numbers
Title: Re: Opamps - Die pictures
Post by: Noopy on January 05, 2024, 09:05:14 am
Without tuning integrated resistors always have high tolerances. The older the process the higher the tolerances. 30% sound quite normal to me.

I assume in one chip the resistors have quite the same tolerance but I wouldn't say in one batch they have similar tolerances at least not back in the days. There was quite some process variation over the wafer.
Title: Re: Opamps - Die pictures
Post by: David Hess on January 05, 2024, 09:20:15 am
Under Fig.1, the text says R values may be +/-30%.
  • is that tolerance between batches, or between the resistors on the same die?
  • is 30% "normal" for untrimmed IC resistors?
It is normal for diffusion resistors, and was even worse in the past.  I did not know that their tolerance had gotten as good as 30%.

The tolerance is for absolute value.  Matching is much better because the resistors are all diffused at the same time and under the same conditions.

Higher value resistors use a different structure, like a JFET in cutoff, so have an even worse tolerance.
Title: Re: Opamps - Die pictures
Post by: AnalogTodd on January 05, 2024, 02:28:41 pm
Batch to batch variation of IC parameters can be massive. Resistor tolerances of +/-30% is normal, and things like transistor betas can often be between half and double their nominal values.

Matching (parameters of one device compared to another close by) on the same die is often fairly tight. Highest precision products will use common centroid (sometimes called cross coupling) of all devices to improve matching even further.

Remember, a fab wants to ship as many wafers as possible, so designers are given extremely wide corners to use as worst-case numbers. It makes the design a lot harder to do, but the target is to make things cost effective on all ends. The wider corners that a design can handle means that wafers that would be otherwise unusable can now be sold.