Author Topic: Opamps - Die pictures  (Read 18817 times)

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Online Noopy

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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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Online 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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Online Noopy

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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!  :-+

Online magic

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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 »
 

Online Noopy

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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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Online 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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Online Noopy

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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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Online 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...

Offline serg-el

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

Online Noopy

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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

Online Noopy

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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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Online 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.
 

Online Noopy

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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.  :-//

Online 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.
 

Online Noopy

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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 »
 

Online Noopy

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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?

Offline David Hess

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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.
 

Online Noopy

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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

Online 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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Online 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...

Online Noopy

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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 :)
 

Online Noopy

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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.

Online 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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