Author Topic: Opamps - Die pictures  (Read 18399 times)

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Offline Noopy

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Opamps - Die pictures
« 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/Opamp05.htm

Thomson LM318

https://www.richis-lab.de/Opamp06.htm

Sescosem SFC2741

https://www.richis-lab.de/Opamp07.htm

Signetics NE5534

https://www.richis-lab.de/Opamp01.htm

 :popcorn:
 
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Offline magic

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Re: Opamps - Die pictures
« Reply #1 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.
 
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Offline Noopy

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Re: Opamps - Die pictures
« Reply #2 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...

Offline Noopy

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Re: Opamps - Die pictures
« Reply #3 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.

Offline David Hess

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Re: Opamps - Die pictures
« Reply #4 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.
 

Offline magic

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Re: Opamps - Die pictures
« Reply #5 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
« Last Edit: June 11, 2020, 07:33:13 pm by magic »
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #6 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

Offline magic

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Re: Opamps - Die pictures
« Reply #7 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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #8 on: June 12, 2020, 08:37:31 am »
You are right. The bias circuit is very different, less complex:



 :-+

Offline David Hess

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Re: Opamps - Die pictures
« Reply #9 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

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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #10 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

LM310 built by Silicon General






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.  :-+




The die is not extremly interesting...

 :popcorn:
 
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Offline magic

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Re: Opamps - Die pictures
« Reply #11 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 ;)
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #12 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.  :-+

Offline magic

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Re: Opamps - Die pictures
« Reply #13 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 ;)
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #14 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?

Offline magic

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Re: Opamps - Die pictures
« Reply #15 on: June 28, 2020, 10:49:57 am »
The NatSemi paper about LM118/318 which I mentioned before.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #16 on: June 28, 2020, 12:05:15 pm »
Of course! Sorry, I was confused somehow.  :-+

Offline SeanB

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Re: Opamps - Die pictures
« Reply #17 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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #18 on: June 28, 2020, 01:11:05 pm »
More coming soon!  :) :popcorn:

Offline David Hess

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Re: Opamps - Die pictures
« Reply #19 on: June 28, 2020, 04:23:22 pm »
Check out Linear Technology application note 16 where Widlar himself describes some details of PNPs on an NPN only process in these types of integrated circuits.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #20 on: July 07, 2020, 08:49:17 pm »
Today I have a comparator, a LM306, for you:








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


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

Offline Hydron

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Re: Opamps - Die pictures
« Reply #21 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).
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #22 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! :-+

Offline magic

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Re: Opamps - Die pictures
« Reply #23 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.
 

Offline macboy

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Re: Opamps - Die pictures
« Reply #24 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

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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #25 on: July 10, 2020, 09:54:41 pm »
Today I have an old LM360 for you:





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

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

 :popcorn:

Offline Noopy

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Re: Opamps - Die pictures
« Reply #26 on: July 25, 2020, 07:28:36 pm »
Today I have a fake NE5534 for you:

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

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




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




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

 :popcorn:

Offline magic

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Re: Opamps - Die pictures
« Reply #27 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?
« Last Edit: July 25, 2020, 08:09:31 pm by magic »
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #28 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...

Offline magic

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Re: Opamps - Die pictures
« Reply #29 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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #30 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.

Offline magic

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Re: Opamps - Die pictures
« Reply #31 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/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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #32 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?

Offline Noopy

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Re: Opamps - Die pictures
« Reply #33 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/Opamp12.htm


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



Offline David Hess

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Re: Opamps - Die pictures
« Reply #34 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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #35 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.






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






More pictures here:

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

 :popcorn:
 
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Offline Noopy

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Re: Opamps - Die pictures
« Reply #36 on: August 20, 2020, 04:01:20 am »


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




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


 :popcorn:
 
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Offline magic

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Re: Opamps - Die pictures
« Reply #37 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?
« Last Edit: August 20, 2020, 07:41:33 am by magic »
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #38 on: August 20, 2020, 07:48:00 am »
At least it was an opamp! :D

Offline magic

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Re: Opamps - Die pictures
« Reply #39 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.
« Last Edit: August 20, 2020, 09:09:14 am by magic »
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #40 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.

 :-//

Offline magic

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Re: Opamps - Die pictures
« Reply #41 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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #42 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:










The second one was built 1988:






That´s odd:



The 1982-LF355 mask revisions were modified often.



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.  :-//

Offline David Hess

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Re: Opamps - Die pictures
« Reply #43 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.
« Last Edit: August 23, 2020, 03:53:50 am by David Hess »
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #44 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...

Offline magic

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Re: Opamps - Die pictures
« Reply #45 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?
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #46 on: August 23, 2020, 07:56:26 am »
I lost my LF155, maybe Noopy could post exact dimensions?

~ 1,87mm x 1,06mm

 :-+

Offline David Hess

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Re: Opamps - Die pictures
« Reply #47 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.
 

Offline magic

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Re: Opamps - Die pictures
« Reply #48 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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #49 on: August 26, 2020, 08:24:17 pm »
A little bit more modern: LF411





Sorry, have no size for this one.




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!




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.

Offline magic

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Re: Opamps - Die pictures
« Reply #50 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]
 
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Offline Noopy

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Re: Opamps - Die pictures
« Reply #51 on: September 23, 2020, 06:00:48 pm »
One more "normal" Opamp, a OP-01:

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




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 ;)






A nice design...




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".

Offline mawyatt

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Re: Opamps - Die pictures
« Reply #52 on: September 23, 2020, 06:59:10 pm »
One more "normal" Opamp, a OP-01:

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...




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,
Research is like a treasure hunt, you don't know where to look or what you'll find!
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Offline magic

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Re: Opamps - Die pictures
« Reply #53 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 ;)
 

Offline David Hess

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Re: Opamps - Die pictures
« Reply #54 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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #55 on: September 23, 2020, 08:14:47 pm »


OP-07  :-+




OP-27, also nice!  :-+


Both use quite a lot transistors.


...taken from AD1139:
https://richis-lab.de/DAC07.htm
 
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Offline David Hess

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Re: Opamps - Die pictures
« Reply #56 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.

 

Offline mawyatt

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Re: Opamps - Die pictures
« Reply #57 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,
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Offline mawyatt

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Re: Opamps - Die pictures
« Reply #58 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,
« Last Edit: September 24, 2020, 07:10:57 pm by mawyatt »
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Offline David Hess

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Re: Opamps - Die pictures
« Reply #59 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.
 

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Re: Opamps - Die pictures
« Reply #60 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,
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Offline mawyatt

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Re: Opamps - Die pictures
« Reply #61 on: September 24, 2020, 11:57:05 pm »


OP-07  :-+




OP-27, also nice!  :-+


Both use quite a lot transistors.


...taken from AD1139:
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,
Research is like a treasure hunt, you don't know where to look or what you'll find!
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Offline David Hess

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Re: Opamps - Die pictures
« Reply #62 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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #63 on: October 14, 2020, 06:59:16 pm »


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.




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




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


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


Offline magic

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Re: Opamps - Die pictures
« Reply #64 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 ;)
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #65 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

Offline magic

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Re: Opamps - Die pictures
« Reply #66 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 :)
« Last Edit: October 14, 2020, 09:54:31 pm by magic »
 
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Offline Noopy

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Re: Opamps - Die pictures
« Reply #67 on: October 15, 2020, 03:03:18 am »

Offline P_Doped

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Re: Opamps - Die pictures
« Reply #68 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.
« Last Edit: October 15, 2020, 11:28:50 pm by P_Doped »
 

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Offline magic

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Re: Opamps - Die pictures
« Reply #70 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.
« Last Edit: October 16, 2020, 07:02:29 am by magic »
 

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Re: Opamps - Die pictures
« Reply #71 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.
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Offline magic

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Re: Opamps - Die pictures
« Reply #72 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.
« Last Edit: October 16, 2020, 08:04:57 am by magic »
 

Offline Zero999

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Re: Opamps - Die pictures
« Reply #73 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.
 

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Re: Opamps - Die pictures
« Reply #74 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?
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Offline magic

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Re: Opamps - Die pictures
« Reply #75 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?
« Last Edit: October 16, 2020, 10:56:42 am by magic »
 

Offline magic

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Re: Opamps - Die pictures
« Reply #76 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.
 

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Re: Opamps - Die pictures
« Reply #77 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.
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Offline magic

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Re: Opamps - Die pictures
« Reply #78 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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #79 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/
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:




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




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.




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.




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.




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




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




Apex also had problems with the bonding process...




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




It´s a Sziklai-Darlington-powerstage.




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:




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

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

 :popcorn:
« Last Edit: October 25, 2020, 10:49:26 pm by Noopy »
 
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Offline RoGeorge

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Re: Opamps - Die pictures
« Reply #80 on: October 25, 2020, 10:27:34 pm »
APEX?!  Like the game?  :D

Offline Noopy

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Re: Opamps - Die pictures
« Reply #81 on: October 25, 2020, 10:28:58 pm »
I´m getting old. Didn´t know there is a game with the name APEX.  ;D :-+

Offline T3sl4co1l

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Re: Opamps - Die pictures
« Reply #82 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
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

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Re: Opamps - Die pictures
« Reply #83 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

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Re: Opamps - Die pictures
« Reply #84 on: November 02, 2020, 10:14:54 pm »


Let´s look into the famous LM709.




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




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

 :-/O
 
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Offline David Hess

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Re: Opamps - Die pictures
« Reply #85 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
 
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Offline Noopy

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Re: Opamps - Die pictures
« Reply #86 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

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.

Offline Noopy

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Re: Opamps - Die pictures
« Reply #87 on: November 05, 2020, 09:00:22 pm »


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




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


 :popcorn:

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Re: Opamps - Die pictures
« Reply #88 on: November 09, 2020, 03:39:34 pm »
Let´s take a closer look into a OPA627!  8)





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




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.




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

 :popcorn:
 
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Offline David Hess

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Re: Opamps - Die pictures
« Reply #89 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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #90 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.  :-//

Offline magic

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Re: Opamps - Die pictures
« Reply #91 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
« Last Edit: November 09, 2020, 08:50:41 pm by magic »
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #92 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:



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

Offline magic

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Re: Opamps - Die pictures
« Reply #93 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.
« Last Edit: November 10, 2020, 10:21:57 am by magic »
 
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Offline Noopy

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Re: Opamps - Die pictures
« Reply #94 on: November 10, 2020, 12:08:45 pm »
Thanks for your interpretation!
A mysterious input stage...  :-/O

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Re: Opamps - Die pictures
« Reply #95 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?
 
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Offline Noopy

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Re: Opamps - Die pictures
« Reply #96 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!  :-+

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Re: Opamps - Die pictures
« Reply #97 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.
« Last Edit: November 10, 2020, 05:35:23 pm by David Hess »
 

Offline Kleinstein

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Re: Opamps - Die pictures
« Reply #98 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.
 

Offline magic

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Re: Opamps - Die pictures
« Reply #99 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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #100 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?  :-+

Offline Noopy

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Re: Opamps - Die pictures
« Reply #101 on: November 13, 2020, 01:08:10 pm »
I have taken pictures of the side of the OPA627-die:




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




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

 :-/O
 
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Offline magic

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Re: Opamps - Die pictures
« Reply #102 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.
 
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Offline Noopy

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Re: Opamps - Die pictures
« Reply #103 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!  :-+

Offline Noopy

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Re: Opamps - Die pictures
« Reply #104 on: November 15, 2020, 05:30:09 am »
Here some older pitctures of a LM741:





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 ;)

Offline Noopy

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Re: Opamps - Die pictures
« Reply #105 on: November 16, 2020, 12:25:22 pm »


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




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




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




The second die is a modified LM741-die.




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

 :-/O
 
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Offline magic

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Re: Opamps - Die pictures
« Reply #106 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.
« Last Edit: November 16, 2020, 06:07:56 pm by magic »
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #107 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:




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).

Offline magic

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Re: Opamps - Die pictures
« Reply #108 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.
 

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Re: Opamps - Die pictures
« Reply #109 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.
 
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Offline magic

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Re: Opamps - Die pictures
« Reply #110 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
 
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Offline djerickson

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Re: Opamps - Die pictures
« Reply #111 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
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #112 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.  :-+

Offline David Hess

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Re: Opamps - Die pictures
« Reply #113 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.
 

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Re: Opamps - Die pictures
« Reply #114 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.  :-+

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Re: Opamps - Die pictures
« Reply #115 on: December 12, 2020, 08:47:36 pm »
(The LT1013 will come soon!)




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




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




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


More pictures here:

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

 :-/O

Offline Noopy

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Re: Opamps - Die pictures
« Reply #116 on: December 22, 2020, 09:52:21 pm »
I'd like to see a photo of LT1013.


Done that:






There is some silicone potting on the die.




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




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




The design dates back to 1987, manufactured in 2000.




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.




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




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




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.




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




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.




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.




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

 8)
 
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Offline David Hess

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Re: Opamps - Die pictures
« Reply #117 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.
 
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Offline magic

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Re: Opamps - Die pictures
« Reply #118 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.
 
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Offline Noopy

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Re: Opamps - Die pictures
« Reply #119 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?

Offline exe

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Re: Opamps - Die pictures
« Reply #120 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?
 

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Re: Opamps - Die pictures
« Reply #121 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.
Believe it or not, pointy haired people do exist!
+++Divide By Cucumber Error. Please Reinstall Universe And Reboot +++
 

Offline magic

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Re: Opamps - Die pictures
« Reply #122 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).


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.
 
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Offline exe

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Re: Opamps - Die pictures
« Reply #123 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 :(.
 

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Re: Opamps - Die pictures
« Reply #124 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.

Offline magic

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Re: Opamps - Die pictures
« Reply #125 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)
« Last Edit: December 23, 2020, 11:48:32 pm by magic »
 
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Offline David Hess

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Re: Opamps - Die pictures
« Reply #126 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.
 
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Offline exe

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Re: Opamps - Die pictures
« Reply #127 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.
 

Offline magic

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Re: Opamps - Die pictures
« Reply #128 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.
« Last Edit: December 24, 2020, 01:22:01 pm by magic »
 
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Offline Noopy

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Re: Opamps - Die pictures
« Reply #129 on: January 12, 2021, 02:09:06 pm »


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




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






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.




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




Here you can see the input stage.




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.




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.




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




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




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


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


 :-/O
 
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Offline exe

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Re: Opamps - Die pictures
« Reply #130 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).
 

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Re: Opamps - Die pictures
« Reply #131 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.

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Re: Opamps - Die pictures
« Reply #132 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 :-//
 

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Re: Opamps - Die pictures
« Reply #133 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...  :-//

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Re: Opamps - Die pictures
« Reply #134 on: January 21, 2021, 08:18:34 pm »
Today I have a comparator, a LM306, for you:








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


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


UPDATE




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






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.




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.  :-+




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).




Lights on!  8)






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
You can see that the output transistor is never switched off completely


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

 :-/O
 
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Offline magic

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Re: Opamps - Die pictures
« Reply #135 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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #136 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.
« Last Edit: January 21, 2021, 09:18:42 pm by Noopy »
 

Offline exe

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Re: Opamps - Die pictures
« Reply #137 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).
 

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Re: Opamps - Die pictures
« Reply #138 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.

Offline Noopy

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Re: Opamps - Die pictures
« Reply #139 on: February 08, 2021, 01:55:07 pm »


Toshiba TA75558 dual-opamp




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?  ;))




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


#

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.




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




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.




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.




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

 :-/O
 
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Offline exe

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Re: Opamps - Die pictures
« Reply #140 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?
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #141 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.

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Re: Opamps - Die pictures
« Reply #142 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

Offline magic

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Re: Opamps - Die pictures
« Reply #143 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.
« Last Edit: February 08, 2021, 07:39:30 pm by magic »
 
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Re: Opamps - Die pictures
« Reply #144 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...


Offline David Hess

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Re: Opamps - Die pictures
« Reply #145 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.

 
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Offline magic

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Re: Opamps - Die pictures
« Reply #146 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.
 
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Offline exe

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Re: Opamps - Die pictures
« Reply #147 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.
 

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Re: Opamps - Die pictures
« Reply #148 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.
 

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Re: Opamps - Die pictures
« Reply #149 on: February 13, 2021, 09:42:06 am »
And so you have to integrate veeeeeery looooooong tracks.  ;D

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Re: Opamps - Die pictures
« Reply #150 on: March 04, 2021, 09:29:52 pm »


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






Intersil Data Book 1979




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




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.






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




BL8007, a typical Intersil naming.




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




There are some differences between the schematic and the die.






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




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




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.




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

 :-/O
 
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Offline magic

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Re: Opamps - Die pictures
« Reply #151 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.
 
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Re: Opamps - Die pictures
« Reply #152 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!  :-+

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Re: Opamps - Die pictures
« Reply #153 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.
« Last Edit: March 04, 2021, 10:27:08 pm by magic »
 

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Re: Opamps - Die pictures
« Reply #154 on: March 04, 2021, 10:37:53 pm »
Right!  :-+

...aaaaand done!  :-/O
 
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Offline magic

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Re: Opamps - Die pictures
« Reply #155 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.
 
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Re: Opamps - Die pictures
« Reply #156 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?






TIC60005






05.T  :-//
Datecode probably 7017






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




That doesn´t really help...  :-//




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




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.




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






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

 :-/O
 
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Offline Noopy

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Re: Opamps - Die pictures
« Reply #157 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...

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Re: Opamps - Die pictures
« Reply #158 on: March 12, 2021, 09:49:22 pm »
 

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Re: Opamps - Die pictures
« Reply #159 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

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Re: Opamps - Die pictures
« Reply #160 on: March 24, 2021, 09:41:35 pm »


National Semiconductor LF356




Interesting: It seems like the LF356 die is exactly the same as the LF355 die (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?  :-//




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


https://www.richis-lab.de/Opamp31.htm
 
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Offline magic

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Re: Opamps - Die pictures
« Reply #161 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.
 

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Re: Opamps - Die pictures
« Reply #162 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.  :-//

Offline magic

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Re: Opamps - Die pictures
« Reply #163 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.
 

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Re: Opamps - Die pictures
« Reply #164 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

Offline David Hess

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Re: Opamps - Die pictures
« Reply #165 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
« Last Edit: March 25, 2021, 05:41:28 pm by David Hess »
 

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Re: Opamps - Die pictures
« Reply #166 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?

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Re: Opamps - Die pictures
« Reply #167 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.
 

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Re: Opamps - Die pictures
« Reply #168 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

Offline magic

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Re: Opamps - Die pictures
« Reply #169 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 :-//
 
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Offline Noopy

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Re: Opamps - Die pictures
« Reply #170 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...

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Re: Opamps - Die pictures
« Reply #171 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). The TIC60005 is one of these.
There is no information about the TOA4709.  :-//





TOA2709




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




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






Two dead transistors and a molten track.  :o




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





TOA4709




A familiar design.






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




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




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



Now some numbers:




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




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




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


 :-/O

Offline exe

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Re: Opamps - Die pictures
« Reply #172 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).

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 :)
 

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Re: Opamps - Die pictures
« Reply #173 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).

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.

Offline magic

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Re: Opamps - Die pictures
« Reply #174 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.

 
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Offline Noopy

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Re: Opamps - Die pictures
« Reply #175 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.  :-+

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Re: Opamps - Die pictures
« Reply #176 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.
 

Offline magic

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Re: Opamps - Die pictures
« Reply #177 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.
 

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Re: Opamps - Die pictures
« Reply #178 on: June 15, 2021, 03:07:31 am »
Looks quite familiar!  :-+ ;D

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Re: Opamps - Die pictures
« Reply #179 on: June 18, 2021, 03:34:41 am »


ML709
Can anybody tell who manufactured these opamps?




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




709 B? A second revision?




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).
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

 :-/O
 
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Offline magic

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Re: Opamps - Die pictures
« Reply #180 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?
 

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Re: Opamps - Die pictures
« Reply #181 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.  :-//

Offline magic

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Re: Opamps - Die pictures
« Reply #182 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
 

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Re: Opamps - Die pictures
« Reply #183 on: June 18, 2021, 09:43:36 am »
Next vacation has to be in Canada!  :-+ ;D

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Re: Opamps - Die pictures
« Reply #184 on: August 19, 2021, 04:59:18 am »


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






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/Opamp35.htm

 :-/O
 
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Offline magic

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Re: Opamps - Die pictures
« Reply #185 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

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/
« Last Edit: August 19, 2021, 06:16:18 am by magic »
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #186 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/

 :-+

Offline dzseki

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Re: Opamps - Die pictures
« Reply #187 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.
HP 1720A scope with HP 1120A probe, EMG 12563 pulse generator, EMG 1257 function generator, MEV TR-1660C bench multimeter
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #188 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/prawez02.htm
vs.
https://www.richis-lab.de/apple.htm

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

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

The design is always a little different.

 :-//

Offline magic

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Re: Opamps - Die pictures
« Reply #189 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
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #190 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.  :-\

Offline magic

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Re: Opamps - Die pictures
« Reply #191 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.
 
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Offline David Hess

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Re: Opamps - Die pictures
« Reply #192 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.
 

Offline Noopy

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Re: Opamps - Die pictures
« Reply #193 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.

Offline dzseki

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Re: Opamps - Die pictures
« Reply #194 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.
HP 1720A scope with HP 1120A probe, EMG 12563 pulse generator, EMG 1257 function generator, MEV TR-1660C bench multimeter
 
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