Author Topic: LM723 die pictures  (Read 8574 times)

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Offline Noopy

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LM723 die pictures
« on: January 21, 2020, 10:59:34 pm »

I decided to open a new thread. I hope that´s ok for everybody. In the 555-thread it would be to far off topic.


In the 555-die-thread Wolfgang asked for pictures of the LM723:
https://www.eevblog.com/forum/projects/some-555-timer-dies/msg2870226/#msg2870226

Done that:






Link to my site:
https://www.richis-lab.de/LM723.htm


I didn´t write very much about it because Wolfgang has already written a lot:
https://electronicprojectsforfun.wordpress.com/power-supplies/a-collection-of-proper-design-practices-using-the-lm723-ic-regulator/

What I realized looking at the die:
It seems that the design is the one you can find in the older datasheet. The schematic in the current datasheet is much more complicated.
I couldn´t figure out when this LM723 was produced but it didn´t look too old to me.
Perhaps I should decap one more LM723...  ::)


Greetings,


Richard
 
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Offline wraper

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Re: LM723 die pictures
« Reply #1 on: January 21, 2020, 11:36:33 pm »
It seems that the design is the one you can find in the older datasheet. The schematic in the current datasheet is much more complicated.
No wonder. On the photo on your website IC looks to be salvaged, sanded, blacktopped and marked again. Look on the tiny holes in ST logo.
 
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Offline Noopy

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Re: LM723 die pictures
« Reply #2 on: January 22, 2020, 04:29:17 am »
Hm, didn´t see that at once but probably you are right.  :-+
I think I have to dedcap one more...  ;D

Offline BravoV

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Re: LM723 die pictures
« Reply #3 on: January 22, 2020, 04:48:56 am »


Have a bunch of these, given by my mentor many-many years ago.

PM me your address, once I get home (currently on travel), I will send you this TO-200 can type 723.

PS : I will be sending used one.
« Last Edit: January 22, 2020, 05:10:26 am by BravoV »
 

Offline Noopy

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Re: LM723 die pictures
« Reply #4 on: January 22, 2020, 06:52:54 pm »
Hello BravoV,

thanks for your offer.  :-+
I will send you my adress.

Offline David Hess

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Re: LM723 die pictures
« Reply #5 on: January 22, 2020, 07:11:04 pm »
It seems that the design is the one you can find in the older datasheet. The schematic in the current datasheet is much more complicated.

The published schematics are often considerably simplified like with the common 324/358 schematics although I understand that there is more than one version of the 723.
 

Offline Noopy

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Re: LM723 die pictures
« Reply #6 on: January 22, 2020, 07:23:10 pm »
The published schematics are often considerably simplified like with the common 324/358 schematics although I understand that there is more than one version of the 723.

In this case the circuit on the die is simpler than the newer shematics.
There are definitely missing a lot of parts on "my" die.

I definitely need a new one…  :)

Offline magic

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Re: LM723 die pictures
« Reply #7 on: January 22, 2020, 10:20:59 pm »
The "new" schematic may be a redesign by National.

Wolfgang's website has an old µa723 application note from Fairchild which shows a schematic very similar to your die.
An even more accurate match is the schematic from Motorola datasheet, but there are a few dumb and confusing errors. The circuit wouldn't ever work as drawn :palm:
Old TI datasheet (before National acquisition) also shows the same schematic as Motorola, without errors.

So there is quite a bit of agreement, and only National sticks out as the weird one. Some datasheets (ST, Philips) have no schematic at all.

And since Texas Instruments absolutely has no taste and looking at their schematics makes me want to throw up, I post corrected Motorola schematic below, which appears to match your die. Enjoy :)

edit
Added the Fairchild schematic for completeness. The only difference I can see is Q9 and Q11 collectors. I have no idea if the original Fairchild die matched the Fairchild schematic or maybe was like everybody else's.

I also don't understand what was the point of connecting Q9 and Q11 collectors to Q4 and Q5. VCC is available in the isolation well right underneath Q4 and Q5, they could have used that if they wanted to.
« Last Edit: January 22, 2020, 10:40:23 pm by magic »
 
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Offline imo

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Re: LM723 die pictures
« Reply #8 on: January 22, 2020, 10:27:55 pm »
FYI - TESLA's MAA723 (with 4 additional resistors) :)
PS: they did DIL14 and metal can
« Last Edit: January 22, 2020, 10:45:36 pm by imo »
 

Offline floobydust

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Re: LM723 die pictures
« Reply #9 on: January 22, 2020, 11:10:17 pm »
The uA723 I believe was originally developed by Bob Widlar in 1967 not sure who developed it (it incorporates his current source). Oldest oldest data I can find is from Fairchild 1971 attached schematic.

Wikipedia: "Widlar's productivity was so great that it has stimulated spurious attributions. A prevalent example erroneously credits him with the design of the μA723 voltage regulator. However, not only was that chip released some two years after Widlar's departure from Fairchild, the circuit employs, and relies on, greatly improved lateral PNP transistors that were not available during the period of Widlar's employment at Fairchild. Credit for the μA723 properly belongs to Darryl Lieux, according to his contemporary (and father of the 741), Dave Fullagar. [48]'

National Semiconductor AN-1 (yes app note #1) November 1967 is all about the LM100 which is quite similar to the uA723 but likely got snarled in patent litigation. The voltage reference, foldback current-limiting all were patented blocks between National and Fairchild, which maybe why the LM100 didn't make it.

edit: 1973 databook here: https://archive.org/details/bitsavers_fairchilddldLinearIntegratedCircuitsDataCatalog_30443462
edit2: 1968 Fairchild uA723 App note http://www.ve6aqo.com/old_manuals.htm
« Last Edit: January 22, 2020, 11:23:42 pm by floobydust »
 

Offline Noopy

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Re: LM723 die pictures
« Reply #10 on: January 23, 2020, 04:28:06 am »
Thanks for all your input!

I will have to collect some more of the LM723-variants.  ;D

Offline magic

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Re: LM723 die pictures
« Reply #11 on: January 23, 2020, 09:00:22 am »
So a few remarks for Wolfgang, if you are reading this ;)

It wasn't exactly the legendary Widlar and, pending further research, the National schematic may not even be true to the original Fairchild design.

And I also doubt it's a buried zener. Looks like any other NPN BE junction visually and the Fairchild appnote (page 1.12) brags about a state of the art process capable of integrating even N-JFETs and capacitors in addition to NPNs and PNPs ;D
 

Offline imo

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Re: LM723 die pictures
« Reply #12 on: January 23, 2020, 09:04:44 am »
No buried zener in 723. And frankly, I doubt there is even a zener as the Vref.
The Vref is quite noisy, I saw 2mV p-p noise there, moreover, Wolfgang confirmed that in his measurements.
PS: I like the 723 (because I built my first PSU around it). On the other hand the stories about its "Vref stability and low noise" are just urban myths, imho.

« Last Edit: January 23, 2020, 09:51:48 am by imo »
 

Offline magic

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Re: LM723 die pictures
« Reply #13 on: January 23, 2020, 09:10:49 am »
Of course there are two zeners: one for Vref and one for bias generation.

The bottom right pad is the buffered Vref output. Next one above is the GND pad. Between them is the 5pF compensation capacitor and two NPNs: Q6 on the right, and D2 on the left. The BE junction is used, just like for D1 elsewhere.
 

Offline imo

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Re: LM723 die pictures
« Reply #14 on: January 23, 2020, 09:23:30 am »
Is that a real zener or a reverse biased transistor junction?
 

Offline magic

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Re: LM723 die pictures
« Reply #15 on: January 23, 2020, 09:33:43 am »
No idea. Looks like any other junction and they don't brag about any special technology in the appnote or datasheet so probably a fake zener, if reverse biased transistors aren't real zeners :)
 
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Offline floobydust

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Re: LM723 die pictures
« Reply #16 on: January 24, 2020, 02:23:21 am »
Noopy, thanks for the archaeological digs.

I find it odd the uA723 won the wars. The 1968 Fairchild App note shows the LM100 schematic...  :-//
Most claims for better performance are due to better IC technology - compensation capacitors, lateral PNP's - but it might have been price or lack of military use that sank the LM105. Application Note 23 - The LM105- An Improved Positive Regulator Robert Widlar January 1969 explains the LM100 limitations, zener noise etc.
Many National Semi IC's came and went, in the 1970's, despite them being fine parts.

About the V reference design, it's mentioned in AN-1 the differences between using a reverse-biased EB junction and avalanche diode, for best tempco. A second goal is compatibility with the IC process so 'surface impurity concentrations' do not need to be specialized. I have a paper databook with AN-1 but could not find on the web.
 

Offline magic

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Re: LM723 die pictures
« Reply #17 on: January 24, 2020, 08:44:04 am »
About the V reference design, it's mentioned in AN-1 the differences between using a reverse-biased EB junction and avalanche diode, for best tempco. A second goal is compatibility with the IC process so 'surface impurity concentrations' do not need to be specialized. I have a paper databook with AN-1 but could not find on the web.
Attached :)

It's included in National's 1973 Linear Applications book and you can find scans of that.

Typing "the first buried zener reference" into web search, I also found this book, which claims that this technology was introduced by the familiar LM199/399.
https://books.google.com/books?id=03JmxpE39N4C&pg=PA7&lpg=PA7&dq=the+first+buried+zener&source=bl&ots=5yhwN6_hv9&sig=ACfU3U0SGgYYnUaYj1lyauVYqAOng6TQHQ&hl=pl&sa=X&redir_esc=y

And back to
what was the point of connecting Q9 and Q11 collectors to Q4 and Q5.
I suppose it's for better power supply rejection. And a side effect is limitation of the regulation amplifier's common mode input range to a diode drop or two above Vref, which means that this tweak was likely not introduced by second sources but by Fairchild themselves. Apparently they concealed it in the documentation to protect their secret sauce :)
 
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Offline BravoV

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Re: LM723 die pictures
« Reply #18 on: January 30, 2020, 04:12:10 pm »
Two of these are on their way to Noopy.  :P

National Semiconductor LM723CH date code 8848, and Fairchild UA723HC date code 8335.

Offline Noopy

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Re: LM723 die pictures
« Reply #19 on: January 30, 2020, 05:31:25 pm »
Nice!

And I found a LM723JC (ceramic package) built by National semiconductor.  :-/O

Offline David Hess

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Re: LM723 die pictures
« Reply #20 on: February 01, 2020, 02:37:13 am »
Below are a pair of Fairchild ceramic packaged 723s in my Tektronix DC505 universal counter which came from NASA's Glenn Research Center.  The photograph shows how I replaced the original Texas Instruments edge wipe plastic DIP sockets which were damaged by the hot operating 723s with collet pins.
« Last Edit: February 01, 2020, 02:39:07 am by David Hess »
 

Offline EEEnthusiast

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Re: LM723 die pictures
« Reply #21 on: February 01, 2020, 03:59:04 am »
Nice hand drawn PCB artwork...
Making products for IOT
https://www.zscircuits.in/
 

Offline Noopy

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Re: LM723 die pictures
« Reply #22 on: February 01, 2020, 07:45:59 am »

And here is the LM723JC:


https://www.richis-lab.de/LM723_01.htm





Looks very different but you can find the similar blocks in the ST Microelectronics LM723CN.

The resistor in the upper right corner looks interesting.  :o



Below are a pair of Fairchild ceramic packaged 723s in my Tektronix DC505 universal counter which came from NASA's Glenn Research Center.  The photograph shows how I replaced the original Texas Instruments edge wipe plastic DIP sockets which were damaged by the hot operating 723s with collet pins.

Nice!  8)

Offline magic

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Re: LM723 die pictures
« Reply #23 on: February 01, 2020, 09:41:43 am »
No, it looks the same. No way in hell that this matches the schematic from current National/TI datasheet.

Look at the reference circuit, it's all the same. Same compensation capacitor near VREF and GND pads, formed by a metal layer over the large collector area of Q6. Same two BE junctions over that collector just north of the capacitor, one is the actual Q6, the other is D2. Same long resistor from D2 anode to ground and another one to Q6 base. Q6 collector again is loaded with a PNP current source and drives a Darlington pair which drives the zener cathode through a resistor. For whatever reason, they moved the bottom transistor of that pair to the left side of the die, near the COMP pad.

It seems they added some base resistance to the current limit transistor and there are only 3 PNPs. There are four, but two of them use the same emitter connection point on the die.

The weird resistor in the upper right seems like part of the biasing circuit, perhaps it's the N-JFET. There are similar structure on a lot of analog opamps and I frankly never quite fully understood how it works.

edit
Not sure if it means that there are two versions of National LM723 or maybe you just bought this part from AliExpress :-DD
« Last Edit: February 01, 2020, 09:44:32 am by magic »
 

Offline imo

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Re: LM723 die pictures
« Reply #24 on: February 01, 2020, 10:04:32 am »
Here is a 723 schematics from electronicprojectsforfun page, with the current sense base resistor (and even more mess):
 

Offline Noopy

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Re: LM723 die pictures
« Reply #25 on: February 01, 2020, 10:08:42 am »
No, it looks the same. No way in hell that this matches the schematic from current National/TI datasheet.

Well perhaps "very different" was a little too hard. The basic schematic could be the same and the blocks are similar arranged but it´s clearly a different ... well ... my english isn´t the best  ;D ... it´s a little bit different.

I´ll have to check the whole circuit as soon as I have more time...

edit
Not sure if it means that there are two versions of National LM723 or maybe you just bought this part from AliExpress :-DD

This one came from ebay...  ;D

Offline magic

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Re: LM723 die pictures
« Reply #26 on: February 01, 2020, 10:11:25 am »
Here is a 723 schematics from electronicprojectsforfun page, with the current sense base resistor (and even more mess):

That's the modern National schematic. And yes, there is a base resistor on the limiter. But it also shows VREF output being connected to the collector of the noninverrting input of the regulation amplifier and that's simply not the case on this die. On the die, regulator amplifier is wired exactly as per the Motorola/TI schematic.

On the other hand, the biasing circuit looks interesting. There are two NPNs connected in a weird way near the JFET, and indeed, it looks like something similar might exist on the die. So perhaps it is some older version of genuine National LM723.

edit
Indeed, the transistors near the JFET look the same, assuming that this wide, snaking thingy is the JFET :)
I can't see anything resembling Q25, though. And the whole reference section is definitely different. For starters, observe that the National schematic shows several PNPs in the reference circuitry, and here there are no PNPs except for the current sources at the top.
« Last Edit: February 01, 2020, 10:30:17 am by magic »
 
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Offline chris_leyson

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Re: LM723 die pictures
« Reply #27 on: February 01, 2020, 11:00:51 am »
Quote
PS: I like the 723 (because I built my first PSU around it). On the other hand the stories about its "Vref stability and low noise" are just urban myths, imho.

Ulrich Rohde published a very low noise regulator circuit using an LM723 and a PNP pass transistor in "Mircrowave and Wireless Synthesizers: Theory and Design". Noise performance turned out to be much better than any of the ultra low noise regulators from National and TI and the 723 ended up as part of a low phase noise crystal oscillator. Circuit below.

 
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Offline imo

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Re: LM723 die pictures
« Reply #28 on: February 01, 2020, 11:21:09 am »
Quote
PS: I like the 723 (because I built my first PSU around it). On the other hand the stories about its "Vref stability and low noise" are just urban myths, imho.
Ulrich Rohde published a very low noise regulator circuit using an LM723 and a PNP pass transistor in "Mircrowave and Wireless Synthesizers: Theory and Design".

You quoted me: Well, experienced voltnuts here (equipped with suitable TE) may build such a source with a "new" 723 off Digikey or Mouser and publish some noise/stability data.
PS: to demonstrate my positive attitude to the 723 - here are 4x "low noise" floating sources (2x15V, 2x5V) I made last fall - with 2x723(15V/60mA/20mA_foldback)+PNP, 723's Vrefs filtered 4k7/220u.
« Last Edit: February 01, 2020, 12:32:18 pm by imo »
 

Offline chris_leyson

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Re: LM723 die pictures
« Reply #29 on: February 01, 2020, 12:22:15 pm »
I used a pair of AC coupled amplifiers either AD797 or LT1028 and I think the overall gain was 40dB to get the noise up to a level I could measure with an HP3585. Used a TI uA723C without an external pass transistor. It would interesting to test a few "new" 723s given the design variations.
 

Offline David Hess

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Re: LM723 die pictures
« Reply #30 on: February 03, 2020, 02:58:53 am »
Nice hand drawn PCB artwork...

For the record, my CAD drawn printed circuit boards look like that also.  Circuit board layouts are about the only place where I made good use of geometry class.

No buried zener in 723. And frankly, I doubt there is even a zener as the Vref.
The Vref is quite noisy, I saw 2mV p-p noise there, moreover, Wolfgang confirmed that in his measurements.
PS: I like the 723 (because I built my first PSU around it). On the other hand the stories about its "Vref stability and low noise" are just urban myths, imho.

The ones I have tested compared very favorably with bandgap references when the 723 was operated as a reference instead of a regulator.  Bandgaps have to be multiplied up or the 723 divided for comparison purposes.

The real advantage should be using the output transistor to operate the 723 at a constant temperature.

« Last Edit: February 03, 2020, 03:05:29 am by David Hess »
 

Offline magic

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Re: LM723 die pictures
« Reply #31 on: February 03, 2020, 08:35:26 am »
These days LM723H seems to cost about as much as LM399 so this oven trick is getting pointless, unless there really is a serious advantage in noise even before filtering.

BTW, I'm not sure why people bother biasing the noninverting input with resistors in those designs. I would leave it open circuit so that the inverting input is pulled firmly to ground by the tail current source and can be used for temperature sensing. It could even be combined into a darlington with the current sense transistor for more gain.

In fact, this technique seems applicable to just about any opamp, so a much more interesting question is if it would work on AD588. The latter is not cheap either, but at least has a fair bit of added functionality which may justify the effort.
« Last Edit: February 03, 2020, 08:36:59 am by magic »
 
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Offline imo

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Offline David Hess

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Re: LM723 die pictures
« Reply #33 on: February 04, 2020, 03:51:09 pm »
These days LM723H seems to cost about as much as LM399 so this oven trick is getting pointless, unless there really is a serious advantage in noise even before filtering.

Why would I need the expensive metal can package?  I am referring to using the 723 output transistor as the heater and the current limit transistor as the temperature sensor.  One example is shown below.

Quote
BTW, I'm not sure why people bother biasing the noninverting input with resistors in those designs. I would leave it open circuit so that the inverting input is pulled firmly to ground by the tail current source and can be used for temperature sensing. It could even be combined into a darlington with the current sense transistor for more gain.

In fact, this technique seems applicable to just about any opamp, so a much more interesting question is if it would work on AD588. The latter is not cheap either, but at least has a fair bit of added functionality which may justify the effort.

If the current mirror which controls the tail current saturates, then all of the connected mirror outputs shut down.  The positive and negative current mirrors used for biasing in the 723 are in a positive feedback loop so both may be affected.

Doing this also removes the Vbe compensation from the error amplifier.
 
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Offline magic

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Re: LM723 die pictures
« Reply #34 on: February 04, 2020, 05:14:17 pm »
If the current mirror which controls the tail current saturates, then all of the connected mirror outputs shut down.  The positive and negative current mirrors used for biasing in the 723 are in a positive feedback loop so both may be affected.
Haven't thought of it :(

That being said, the lower current mirror of µA723 has no other outputs so no problem here. And IMO the fault will not propagate to the upper mirror, because the saturated mirror's input will not go high impedance.

In this particular mirror, I think the "driver" transistor Q9 will take on generation of the missing half of Q13 emitter current and feed it there directly through Q13 base, restoring normal operating point of Q10 and permitting sinking of all Q7 output.

I concede that this doesn't generalize to arbitrary opamps as easily as I hoped.

Doing this also removes the Vbe compensation from the error amplifier.
Sure, the idea is to use the input stage of an opamp as a temperature sensor / regulator :)
 

Offline David Hess

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Re: LM723 die pictures
« Reply #35 on: February 04, 2020, 06:14:22 pm »
If the current mirror which controls the tail current saturates, then all of the connected mirror outputs shut down.  The positive and negative current mirrors used for biasing in the 723 are in a positive feedback loop so both may be affected.
Haven't thought of it :(

That being said, the lower current mirror of µA723 has no other outputs so no problem here. And IMO the fault will not propagate to the upper mirror, because the saturated mirror's input will not go high impedance.

The schematic I checked showed one other output ... to drive the positive current mirrors in parallel with the startup circuit through Q25 thereby controlling the available current to the input of the bottom current mirror, hence the positive feedback.

Quote
In this particular mirror, I think the "driver" transistor Q9 will take on generation of the missing half of Q13 emitter current and feed it there directly through Q13 base, restoring normal operating point of Q10 and permitting sinking of all Q7 output.

As mentioned previously, that schematic is wrong in some details so I am not sure if what you would suggest would work or not.  Unlike the example I gave, I would probably not be as clever and instead use an external error amplifier for the thermal control for more gain.

Quote
I concede that this doesn't generalize to arbitrary opamps as easily as I hoped.

Some operational amplifiers do weird things if the input common mode range is exceeded or the output is allowed to saturate.  Duals and quads where the bias circuitry is shared can be especially problematic with the condition of one amplifier affecting others.  More modern parts tend to be designed to at least behave benignly.

Doing this also removes the Vbe compensation from the error amplifier.

Sure, the idea is to use the input stage of an opamp as a temperature sensor / regulator :)[/quote]

It will also pick up the saturated temperature coefficient of the current mirror output.  Offhand I do not remember if that would add to or subtract from the Vbe temperature coefficient.
 

Offline magic

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Re: LM723 die pictures
« Reply #36 on: February 04, 2020, 09:30:35 pm »
Oh, Q25, forgot about that one. It's unique to National and not even present in the one National chip we have seen so far. But I think it's not a problem, I think the mirror will work all right thanks to Q9. A subtle issue may occur in chips following the original design, because diverting current from Q11 to Q9 will reduce standing current in one of the VREF output transistors, likely affecting VREF load regulation.

I assume that saturation tempco is low enough to be ignored. For what it's worth, ZTX689B datasheet shows about +25mV going from 25°C to 100°C at 1A. That's 15% loss of gain. Almost no difference at low currents and almost no difference at -55°C - not sure what to think of that, but who cares.

You are perhaps right that I'm trying to be too clever, but I like the minimalism in elimination of those external resistors on IN+ :)
 

Offline Noopy

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Re: LM723 die pictures
« Reply #37 on: February 08, 2020, 04:55:16 pm »
I got a LM723J:

https://richis-lab.de/LM723_02.htm

Wolfgang said the LM723CJ is the consumer version and the LM723J shows less drift.

Actually the die looks very different:



It even has testpads!

Perhaps it´s only one of the newer (complexer) designs or the LM723J is really different to the LM723CJ...
I think I need one or two more of this LM723...  ;D

Offline magic

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Re: LM723 die pictures
« Reply #38 on: February 12, 2020, 08:34:18 am »
This might be the new National circuit. And look at that green snake meandering over isolation diffusions; I was wondering how they are going connect Q10 with Q25 on the opposite side of the die and there you go :)

Now, where's the reference diode and what are those combs on the left side? Schematic suggests capacitors? :-//

Those test pads seem to be Zener zaps. They are connected to reverse biased BE junctions and resistors in parallel with them. Is this thing really calibrated in production?
« Last Edit: February 12, 2020, 08:45:03 am by magic »
 

Offline Noopy

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Re: LM723 die pictures
« Reply #39 on: February 12, 2020, 11:16:00 pm »
This might be the new National circuit. And look at that green snake meandering over isolation diffusions; I was wondering how they are going connect Q10 with Q25 on the opposite side of the die and there you go :)

That resistor is really freaky!  ;D


Now, where's the reference diode and what are those combs on the left side? Schematic suggests capacitors? :-//

Those test pads seem to be Zener zaps. They are connected to reverse biased BE junctions and resistors in parallel with them. Is this thing really calibrated in production?

Have to do some more research. Right now it´s a bit to late...

Offline magic

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Re: LM723 die pictures
« Reply #40 on: February 13, 2020, 07:44:30 am »
I'm starting to wonder if the whole reference section could actually be a bandgap cell :scared:

For starters, there is no DC connection between D2 and anything else on the schematic, only some AC coupling. This wouldn't be the first time a datasheet schematic is wrong, but I'm not sure what the missing connection could be and where to find it on the die.

On the other hand, Q21, Q22, R14, R15 could be a bandgap reference. Note that Q22 consists of 10 identical copies of Q21.
Q19, Q20 current mirror attempts to establish equal current through them, Q19 collector drives the emitter followers Q6, D5, Q4, Q5 which regulate VREF and indirectly control Q21, Q22 base voltage. This is how bandgaps work AFAIK.

Note that the VREF node is driven by Q5 emitter and I don't really see other feedback path to Q5 base besides the above.

It remains a mystery what Q23, Q24 are doing. Some thermal compensation?
And I glossed over R8. :wtf:

edit
It has to be a bloody bandgap. Zener fanboys are running for cover :-DD
« Last Edit: February 13, 2020, 08:09:14 am by magic »
 
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Offline Noopy

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Re: LM723 die pictures
« Reply #41 on: February 13, 2020, 11:05:56 pm »
Interesting!

I have to do some more research regarding the LM712. But at the moment you know much more about the LM723 than me...  :-+:popcorn:

Offline imo

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Re: LM723 die pictures
« Reply #42 on: February 13, 2020, 11:54:27 pm »
No buried zener in 723. And frankly, I doubt there is even a zener as the Vref.
:D
 

Offline David Hess

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Re: LM723 die pictures
« Reply #43 on: February 14, 2020, 04:43:11 am »
I'm starting to wonder if the whole reference section could actually be a bandgap cell :scared:

I have been told that some versions used a bandgap instead of a zener reference.

Quote
For starters, there is no DC connection between D2 and anything else on the schematic, only some AC coupling. This wouldn't be the first time a datasheet schematic is wrong, but I'm not sure what the missing connection could be and where to find it on the die.

I have noticed that before many times now.  I think the schematic is wrong.
 

Offline magic

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Re: LM723 die pictures
« Reply #44 on: February 14, 2020, 08:59:21 am »
The schematic looks mostly right so far. VREF is driven by Q5, the NPN right next to the bias PNPs. Q5 base is driven by Q4 emitter, Q4 has D5 embedded on its collector (there seems to be a tiny fractional collector shorted to the base by a patch of metal) and that is driven by Q6, whose base is a high impedance node between Q21 and Q19 collectors. Long story short, VREF is two diode drops above the voltage between Q19 and Q21. And this voltage is determined solely by the ratio of Q21 and Q22 currents due to the PNP mirror above them. That's a bandgap cell, and it seems to control the output exclusively.

I assume that Q4 and Q6 are substrate PNPs and the yellow-brown stuff around their emitters is just bulk epitaxial layer silicon with no buried layer underneath (buried layer seems to show up as red-brown). That's consistent with grounded-collector PNPs I have seen elsewhere. But surface P diffusions (NPN bases) are visually almost identical to bulk silicon here, so maybe I'm wrong and it is actually a P diffusion which acts as the GND collector and it covers almost the whole island and makes contact with P isolation diffusions surrounding it to rid itself of the incoming current :-//

I don't quite understand the nature of the three objects hanging off the left collector of the split PNP at the top. One of them ought to be D2. Perhaps D2 is a patch of N+ over the large grounded P collector of Q4, assuming that Q4 has a surface collector. Then there is that green strip (green is N+ elsewhere) which leaves the isolation island and apparently connects to GND metal. It could be that it activates when Q4 collector / D2 anode rises 0.7V above ground due to P diffusion's resistance and shunts the current to ground. No idea :-//

By they way, if you wonder what's the point of D2 if the chip uses a bandgap reference, it might serve to reduce voltage across the compensation capacitors, which are presumably of "reverse-biased BE junction" type, and prevent breakdown. But I'm not sure, those combs look totally weird.
« Last Edit: February 14, 2020, 09:05:12 am by magic »
 

Offline BravoV

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Re: LM723 die pictures
« Reply #45 on: February 14, 2020, 09:02:14 am »
I'm starting to wonder if the whole reference section could actually be a bandgap cell :scared:

I have been told that some versions used a bandgap instead of a zener reference.

Which version exactly ?

Offline David Hess

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Re: LM723 die pictures
« Reply #46 on: February 16, 2020, 04:57:52 pm »
I'm starting to wonder if the whole reference section could actually be a bandgap cell :scared:

I have been told that some versions used a bandgap instead of a zener reference.

Which version exactly ?

Foreign knock offs maybe?  The comment was made in connection with why some 723s are much noisier than others.  I never found a schematic for one with a bandgap reference or at least one that I recognized as such.
 

Offline Wolfgang

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Re: LM723 die pictures
« Reply #47 on: February 16, 2020, 08:42:44 pm »
So a few remarks for Wolfgang, if you are reading this ;)

It wasn't exactly the legendary Widlar and, pending further research, the National schematic may not even be true to the original Fairchild design.

And I also doubt it's a buried zener. Looks like any other NPN BE junction visually and the Fairchild appnote (page 1.12) brags about a state of the art process capable of integrating even N-JFETs and capacitors in addition to NPNs and PNPs ;D

Hi,

have you seen Noopy's LM723J die photos ? They look substantially different from the consumer stuff.
https://www.richis-lab.de/LM723.htm
The J/833 parts are a lot more stable than the CN versions, I still have no info how they have been made.
 

Offline magic

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Re: LM723 die pictures
« Reply #48 on: February 16, 2020, 11:00:45 pm »
Hi, we discussed this new die a few days ago. It appears to match the schematic from National datasheet and I think it's a bandgap, crazy as it sounds.

Look at transistors Q21 and Q22, the latter made of ten paralleled Q21 emitters, and the resistors between them. If I understand correctly, that's exactly what a bandgap reference is supposed to look like. Read my post from February 14th, where I explained why I think that VREF output is determined solely by a need to keep Q21 and Q22 currents equal (maybe up to a constant, not sure what the influence of R8 is). This is achieved by driving their bases to some appropriate level and no higher.

And I just calculated from the values of the resistive divider that with VREF=7.15V their base voltage is about 1.23V, go figure.*

We have also seen a different National part (or so Noopy's eBay vendor said ;)), which used a similar bias generator to this one but otherwise was identical with all the mainstream xx723s. Perhaps an older National version, maybe a fake, or maybe they really put different dice in the J and CJ versions :-//

You can verify which version you have by testing resistance from VREF to GND. It should show open circuit on the classic design chips and about 15kΩ on this National weirdo.


*There is a bit of influence by Q23 and Q24 collector current. This part of the circuit is completely above my head, but I think it makes little difference because emitter resistors are relatively high and base voltages are only 600~650mV above ground. Maybe I should do the math instead of guessing but I'm lazy ::)
« Last Edit: February 16, 2020, 11:13:15 pm by magic »
 

Offline Wolfgang

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Re: LM723 die pictures
« Reply #49 on: February 16, 2020, 11:50:30 pm »
There is one pragmatic point that speaks against a bandgap version. The 7.something volts is exactly what you would choose for a Zener with minimum tempco. For a bandgap, you can make any voltage, and with a lower voltage you would be able to run the chip at lower supply voltages too, widening its market (723 minimum 10V is not ideal for many cases). So I still doubt the did a bandgap.

723 clones with improved data (SG3532,...) did use bandgaps, but they also offered a much lower minimum supply voltage.

The remedy would be to consult the inventors, bit I'm afraid all them have already moved over to the eternal soldering grounds.
 

Offline magic

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Re: LM723 die pictures
« Reply #50 on: February 17, 2020, 08:47:36 am »
But they weren't drop-in replacements. National LM723 is a drop-in replacement for µA723 and could readily be sold to any µA723 user desiring freedom from zener walkout or whatever ;)

And actually, there are people who complained about just that on TI support forum a few years ago.


Perhaps I'm wrong, perhaps that bandgap circuit is somehow sneakily used to compensate a zener or maybe it isn't even a bandgap at all. But we have the datasheet and we have the die image and yet no concrete alternative theory of operation has been proposed so far, despite a few people stating they don't believe that this chip uses a bandgap reference ;)

Noopy, do you have a full resolution pic of the area between the compensation pad and those two lateral PNPs next to it? Something like the closeup of the test pads that's on your website.
« Last Edit: February 17, 2020, 09:13:55 am by magic »
 

Offline imo

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Re: LM723 die pictures
« Reply #51 on: February 17, 2020, 09:08:48 am »
I think a zener is more process steps in manufacturing and less yield. The bandgap is more compatible with the processes they had. When you look at the dies of the Vrefs with zeners you may see the zeners are always pretty visible structures there.
 

Offline magic

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Re: LM723 die pictures
« Reply #52 on: February 17, 2020, 09:24:10 am »
Two of Noopy's dice appear to use an NPN base emitter junction as a zener. That's no rocket science.

You are talking about high-spec chips using subsurface zeners. I linked a source which claims that this technology was introduced for the first time in LM199 in mid-1970s, while µA723 was introduced in late 60s.
 

Offline imo

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Re: LM723 die pictures
« Reply #53 on: February 17, 2020, 09:41:00 am »
You can verify which version you have by testing resistance from VREF to GND. It should show open circuit on the classic design chips and about 15kΩ on this National weirdo.

15xMAA723 DIL14 resistance between pin 6 (+Vref) and 7 (Gnd)

15x 110-115kOhm (34401A kOhm)
14x 1.85-1.89MOhm 1x0.85MOhm (34401A Mohm).
« Last Edit: February 17, 2020, 10:45:19 am by imo »
 

Offline magic

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Re: LM723 die pictures
« Reply #54 on: February 17, 2020, 10:19:47 am »
 :palm: :palm: :palm:

Right, there is a parasitic PN junction from the 100Ω resistor on VREF to VCC. But that's still considerably more than 15kΩ, good enough :)

The 190kΩ outlier may be an autoranging artifact. You will likely get a different reading if you force the megaohm range.
 

Offline imo

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Re: LM723 die pictures
« Reply #55 on: February 17, 2020, 10:37:04 am »
Fixed above.
 

Offline Wolfgang

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Re: LM723 die pictures
« Reply #56 on: February 17, 2020, 11:18:57 am »
But they weren't drop-in replacements. National LM723 is a drop-in replacement for µA723 and could readily be sold to any µA723 user desiring freedom from zener walkout or whatever ;)

And actually, there are people who complained about just that on TI support forum a few years ago.


Perhaps I'm wrong, perhaps that bandgap circuit is somehow sneakily used to compensate a zener or maybe it isn't even a bandgap at all. But we have the datasheet and we have the die image and yet no concrete alternative theory of operation has been proposed so far, despite a few people stating they don't believe that this chip uses a bandgap reference ;)

Noopy, do you have a full resolution pic of the area between the compensation pad and those two lateral PNPs next to it? Something like the closeup of the test pads that's on your website.

Complaints about drift were common a few years ago, thats true. BUT, it only applied to the consumer version, and it was attributed to some surface charge topic, because you could "heat them out" using elevated temperatures. My guess: New, fast process, cheaper to make, but not as good as the old one (or only after some months of service). Even the higher drift is within specs. TI recommended the MIL version as an alternative.
 

Offline Noopy

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Re: LM723 die pictures
« Reply #57 on: February 17, 2020, 04:40:15 pm »
Coincidentally (and with thanks to floobydust) I have a MIL723 for you:

https://richis-lab.de/LM723_03.htm

 8) :popcorn:







But I don´t know who built this one...

 
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Offline Wolfgang

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Re: LM723 die pictures
« Reply #58 on: February 17, 2020, 04:55:01 pm »
... this one looks like a fake part to me. The military never made parts with a C temperature class.
In TO-99 the MIL parts were suffixed -HM or HJ, IIRC.
« Last Edit: February 17, 2020, 07:58:10 pm by Wolfgang »
 

Offline magic

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Re: LM723 die pictures
« Reply #59 on: February 17, 2020, 07:20:34 pm »
No parasitic diode from VREF to VCC :-+

Somebody saved himself the headache of routing a few ground traces and used the substrate :)

H suffix indicates the package, C the temperature class. There are LM723CH still available at Mouser. But MIL-C, yeah, what's that :-//
« Last Edit: February 17, 2020, 07:26:45 pm by magic »
 

Offline floobydust

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Re: LM723 die pictures
« Reply #60 on: February 17, 2020, 08:55:20 pm »
Thanks to Noopy for popping the hood on that MIL723 which has been in my parts bin for decades.
I don't remember where I got it from. Gold leads and bonding wires, it's not a fake by modern standards. But the marking is plain and no logo. If I did buy it, must have been from Poly-Paks around 1977 and they were notorious for selling blems and rejects. Have to compare die fonts to see who made it.
I checked ads and could not find it. Did see ads for the LM300 sold as a "super 723".

Signetics NE550 almost identical to LM723 but a lower reference voltage 1.6V despite a zener being there?
I wonder how IC designs were licensed back there. The shenanigans with the reference must be over patent issues, or to get a little better numbers off the datasheet for sales.
« Last Edit: February 17, 2020, 09:04:24 pm by floobydust »
 

Offline Wolfgang

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Re: LM723 die pictures
« Reply #61 on: February 17, 2020, 09:19:48 pm »
What speaks for a fake is the unlabeled chip and the MIL/consumer temp range combo.
Maybe east block ? Or some spec-missing surplus ? But then the chips would at least have a label.
 

Offline Noopy

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Re: LM723 die pictures
« Reply #62 on: February 17, 2020, 09:23:09 pm »
What speaks for a fake is the unlabeled chip and the MIL/consumer temp range combo.
Maybe east block ? Or some spec-missing surplus ? But then the chips would at least have a label.

I have already opened a MAA723 (Tesla). That one looks different.
Coming soon...
 
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Offline Wolfgang

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Re: LM723 die pictures
« Reply #63 on: February 17, 2020, 09:35:10 pm »
Thanks to Noopy for popping the hood on that MIL723 which has been in my parts bin for decades.
I don't remember where I got it from. Gold leads and bonding wires, it's not a fake by modern standards. But the marking is plain and no logo. If I did buy it, must have been from Poly-Paks around 1977 and they were notorious for selling blems and rejects. Have to compare die fonts to see who made it.
I checked ads and could not find it. Did see ads for the LM300 sold as a "super 723".

Signetics NE550 almost identical to LM723 but a lower reference voltage 1.6V despite a zener being there?
I wonder how IC designs were licensed back there. The shenanigans with the reference must be over patent issues, or to get a little better numbers off the datasheet for sales.

The large headroom requirement is certainly one of the downsides of the original 723. All clones used a lower reference voltage (down to 1.2V), so you could make, e.g., a 2.5V regulator fed from 5V supplies, impossible with an original 723 with a 7.2V Zener in it.
 

Offline floobydust

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Re: LM723 die pictures
« Reply #64 on: February 18, 2020, 04:02:39 am »
I notice the extra pad, perhaps for burn-in. I'm not sure what transistor it connects to and why you'd bother there.
Looking at µA723 aerospace vendors, the usual Fairchild, Philips, TI were the big manufacturers. Raytheon Systems LTD Weapons, Intersil, AMD, Bunker Ramo, Adelco Elektronik, Lockheed Martin were lesser known sources for the 723.
 

Offline magic

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Re: LM723 die pictures
« Reply #65 on: February 18, 2020, 08:09:06 am »
The extra pad is Vz which is missing on the metal can package. It's not a transistor but a zener.

Green is P, grey is N, you can imagine how that works. The N also makes emitter balancing resistors for the power tranny.
« Last Edit: February 18, 2020, 08:14:07 am by magic »
 

Offline floobydust

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Re: LM723 die pictures
« Reply #66 on: February 18, 2020, 08:21:43 pm »
I'm not fluent in die-> transistor interpretation, especially seeing 8 mask layers.
Added "History of Semiconductor Engineering" by Dr. Bo Lojek to my reading list. Quote the hate:
"A Fairchild researcher trained a frog to jump at the sound of a bell. The researcher measured the distance the frog would jump, then removed the frog’s legs and rang the bell again. The frog did not move, thus proving the Fairchild R&D group hypothesis that removing a frog’s legs deafens the animal.”  Robert J. Widlar, describing Fairchild’s R&D group in 1967.
 

Offline Wolfgang

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Re: LM723 die pictures
« Reply #67 on: February 18, 2020, 08:32:06 pm »
I'm not fluent in die-> transistor interpretation, especially seeing 8 mask layers.
Added "History of Semiconductor Engineering" by Dr. Bo Lojek to my reading list. Quote the hate:
"A Fairchild researcher trained a frog to jump at the sound of a bell. The researcher measured the distance the frog would jump, then removed the frog’s legs and rang the bell again. The frog did not move, thus proving the Fairchild R&D group hypothesis that removing a frog’s legs deafens the animal.”  Robert J. Widlar, describing Fairchild’s R&D group in 1967.
A classic. Another one:
A patient consults a doctor and tries to persuade the doctor that he is alread dead. The doctor uses all kinds of scientific and pragmatic arguments that this could not be the case, like the patient breathes, has an audible heratbeat, can roll his eyes and move, talk and what not - to no avail, the patient insists that he is dead. Then, as a last result, he asked the patient: do dead people bleed ? The patient thinks a while, and then replies: no, dead people do not bleed. In a swift movement, the doctor takes a small  knife and makes a small cut in one of the patients fingers - and a stream of blood comes out. The doctor says: See - you cannot be dead. The patient says: No - I just was wrong saying that corpses dont bleed.
« Last Edit: February 18, 2020, 09:25:23 pm by Wolfgang »
 

Offline magic

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Re: LM723 die pictures
« Reply #68 on: February 18, 2020, 09:16:16 pm »
I'm not fluent in die-> transistor interpretation, especially seeing 8 mask layers.
I don't need to understand anything, I know it has to be a zener from the pinout :-DD

A quick glance at obviously-NPN-transistors reveals that grey on green is emitter on base. This is a BE junction intended for reverse biasing, though actually no one can stop you from forward biasing it externally if that's your thing ;)
 

Offline Noopy

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Re: LM723 die pictures
« Reply #69 on: February 19, 2020, 07:25:48 pm »
Here we have a (three) Tesla MAA723:

https://www.richis-lab.de/LM723_04.htm




Three different packages and date codes but always the same die:





Hey there are cracks all over the surface!  ???
 
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Offline Noopy

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Re: LM723 die pictures
« Reply #70 on: February 20, 2020, 10:37:59 pm »
And here a very old LM723CN:

https://www.richis-lab.de/LM723_05.htm








It´s the same die as in the LM723CJ:

https://www.richis-lab.de/LM723_01.htm


Some corrosion on some bondpads:

 
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Offline magic

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Re: LM723 die pictures
« Reply #71 on: February 21, 2020, 10:34:58 am »
A small analysis of the National bandgap circuit.

The divider driving Q21,Q22 has total resistance of 14.879kΩ including 2.58kΩ on the lower side. Q21,Q22 base voltage is therefore roughly 1.240V. Not sure why I got 1.23V before.

Q24 base is then 710mV, yielding Q24 current of give or take 100µA for an additional voltage drop of 40mV on R16 and actual Q21 voltage closer to 1.23V. Ha, I was right even if I got my math wrong :) Q23 influence is even less and both are insignificant in the grand scheme of things.

R15 including the trimmable part is 12kΩ and voltage across that is circa 600mV. We estimate 50µA combined Q21,Q22 current.

Assuming 1µA base current in Q20, we get 2mV drop across R8 and therefore mirror gain of +6%. That's insignificant, probably on the order of base current errors. The mirror is unity gain. (The PNPs themselves are identical).

Each of Q21,Q22 has 25µA current and therefore about 1mS transconductance / 1kΩ intrinsic emitter resistance. Q22 has an additional 2kΩ of physical resistance in R14.

Assuming 50V Early voltage for Q21 and Q19 (pulled outta my ass for easy calculations) we get 1MΩ combined collector impedance on their junction node / Q6 base.

Let's do the loop gain. Rising Q21 Vbe by 3mV we get 3µA extra current in Q21 and 1µA in Q22. That's 4µA total and 48mV extra across R15. So for a 51mV rise of Q21,Q22 base wrt ground we get 3µA rise in Q21 and 1µA in Q22 and therefore -2µA at the Q21,Q19 junction and a -2V shift of Q6 base voltage and the VREF node.

That's not a lot :-//

Could it be that this circuit just compensates a zener? But how would that work :wtf:
 
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Offline magic

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Re: LM723 die pictures
« Reply #72 on: March 01, 2020, 08:03:38 pm »
I assume that Q4 and Q6 are substrate PNPs and the yellow-brown stuff around their emitters is just bulk epitaxial layer silicon with no buried layer underneath (buried layer seems to show up as red-brown).
I learned that this is wrong and that buried layer is not visible externally. The only sign of its presence is a slight vertical depression on the surface of the epitaxial layer and even that is shifted vertically with respect to the real location of the buried structures. This phenomenon is known as "buried layer pattern shift" and a lot has been written about it because it's a nuisance for IC fabs - it makes it difficult to align surface features to the buried ones.

maybe I'm wrong and it is actually a P diffusion which acts as the GND collector and it covers almost the whole island and makes contact with P isolation diffusions surrounding it to rid itself of the incoming current :-//
This appears to be the case. The mustard colored areas at the perimeter of isolation islands have to be P diffusions produced in the same step as NPN bases. I really tried to find some confirmation in literature available online and failed, except for this somewhat ambiguous suggestion in "Analysis and Design of Analog Integrated Circuits":

Quote
The terraced effect on the surface of the device results from the fact that additional oxide is grown during each diffusion cycle, so that the oxide is thickest over the epitaxial region, where no oxide has been removed, is less thick over the base and isolation regions, which are both opened at the base mask step, and is thinnest over the emitter diffusion.

Additional evidence is the fact that the long green N+ silicon resistor on the LM723J die appears to overlap slightly some isolation islands and yet makes no electrical contact with them, so it needs to have some grounded P silicon below it for isolation. Also, the MIL723 die has places where a P resistor connects an NPN base with the perimeter of the isolation island and it all looks perfectly smooth.

Armed with this knowledge we can have another look at the National LM723J and its D2 diode.

[attachimg=1]

On the right, we see the emitter and base of Q6, covered by metal and surrounded by "mustard", which has to be a surface diffused collector extending all the way to the isolation diffusion around the island. Above Q6, an N+ diffusion is made into the collector and part of it branches off to the right and crosses two vertical metal traces. I thought that it connects with the metal on the far right, which is GND, but with some magnification of the image it becomes apparent that it actually does not.

Since the N+ diffusion is fed constant current from Q3, it forms a zener diode with the grounded P silicon below (D2 on the National schematic) and assumes a fixed potential of a few volts above ground. So what's the point of the stub extending to the right? The stub is just long enough to leave the isolation island of Q6 and reach an isolation diffusion, which has higher concentration of P dopant than Q6 collector. Higher doping is known to reduce breakdown voltage (see Linear AN-82, buried zeners chapter) and I presume it's the reason why D2 has lower breakdown voltage than D1, which is a plain BE junction.

The metal connection to D2 cathode branches to the left and connects with structures in another isolation island. It appears to be connected to the bulk of the island and a P diffusion in it. The P diffusion has a comb-like N+ diffusion inside, forming a base-emitter diode. Reverse bias across this diode is no more than 5.9V (VREF minus two diode drops) and almost zero if we assume that D2 voltage is 5.7V. Therefore the chance that this diode forms some super-fancy large area zener appears rather slim. Furthermore, such zener would be in series with the wimpy D2 zener, so what's the point?

I think that the "comb" really is a compensation capacitor and nothing more. This is a bandgap chip, plain and simple. The datasheet schematic checks out 100% and it all makes sense.

Let's do the loop gain. Rising Q21 Vbe by 3mV we get 3µA extra current in Q21 and 1µA in Q22. That's 4µA total and 48mV extra across R15. So for a 51mV rise of Q21,Q22 base wrt ground we get 3µA rise in Q21 and 1µA in Q22 and therefore -2µA at the Q21,Q19 junction and a -2V shift of Q6 base voltage and the VREF node.

That's not a lot :-//
Yep, loop gain is only some 20~40dB. But current through Q5 is almost 0.5mA due to the resistive divider, so Q5 emitter output impedance is some 50~70Ω depending on temperature. Then, closed loop output impedance is a few ohms or maybe a bit under one ohm. I can believe it.
« Last Edit: March 02, 2020, 06:04:45 am by magic »
 
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Offline Noopy

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Re: LM723 die pictures
« Reply #73 on: March 03, 2020, 08:37:18 pm »
Thanks magic for your very interesting analysis!  :-+


I have a new LM723-variant!  ;D

Thanks to BravoV I was able to take a look at the Fairchild UA723:







=> https://www.richis-lab.de/LM723.htm
=> https://www.richis-lab.de/LM723_06.htm

 :popcorn:

Edit: I´m sorry for my german english.  ;D
« Last Edit: March 04, 2020, 04:22:25 am by Noopy »
 
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Offline BravoV

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Re: LM723 die pictures
« Reply #74 on: March 04, 2020, 12:00:20 pm »
Thanks and credit should goes to you, Noopy, I really enjoy it.  :clap:  :-+

As I'm noob at interpreting from the die shot, so how this Fairchild UA723 differs from others ?

Offline magic

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Re: LM723 die pictures
« Reply #75 on: March 04, 2020, 04:33:35 pm »
I didn't review every nook and cranny but topology seems equivalent to all the others.

Notably, Q11 is powered from Q4 and O9 from Q5, which means that Fairchild lied on their schematic.

Either that or we need an older Fairlchild die. But no, they lied. It totally makes sense to wire things that way. Q9 and Q11 provide bias current for Q4 and Q5 while Q4 and Q5 improve PSRR for Q9 and Q11. Win win.
 
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Offline Noopy

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Re: LM723 die pictures
« Reply #76 on: March 04, 2020, 06:34:01 pm »
Thanks and credit should goes to you, Noopy, I really enjoy it.  :clap:  :-+

It was me a pleasure!  :)


As I'm noob at interpreting from the die shot, so how this Fairchild UA723 differs from others ?

magic is more familiar with the LM723. He can do better analysis.  :-+

Offline Noopy

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Re: LM723 die pictures
« Reply #77 on: March 09, 2020, 05:31:52 pm »
News! Surprising news!  ;D

BravoV has also sent me a National Semiconductor LM723CH.

With a "C" we would expect a simple die like in the LM723CN or in the LM723CJ:
https://www.richis-lab.de/LM723_05.htm
https://www.richis-lab.de/LM723_01.htm

Wrong! In the LM723CH there is the same die as in the LM723J:



Sorry, the picture is a bit blurred. Didn´t get it better…

Whole story here: https://www.richis-lab.de/LM723_07.htm

Perhaps the die was sorted out because of bad characteristics but it was ok for a C-variant?
Perhaps they had a lot of the complexer dies and it was cheaper to put them also in the C-package?


Overview for those reading only the last post of this thread: https://www.richis-lab.de/LM723.htm
 
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Offline magic

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Re: LM723 die pictures
« Reply #78 on: March 09, 2020, 05:43:57 pm »
Maybe they just switched to this new design at some point.

TI still makes National's LM723 so one could see what current production chips look like, but they are only available in metal cans and at stupidly high price. Milking the last remaining aerospace customers or whatever they do.
 

Offline Noopy

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Re: LM723 die pictures
« Reply #79 on: March 09, 2020, 05:49:19 pm »
Maybe they just switched to this new design at some point.

TI still makes National's LM723 so one could see what current production chips look like, but they are only available in metal cans and at stupidly high price. Milking the last remaining aerospace customers or whatever they do.

The LM723CH has a date code 8848.
Possible...
Perhaps I find a newer one to compare…  :)

Offline schmitt trigger

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Re: LM723 die pictures
« Reply #80 on: March 09, 2020, 05:52:22 pm »
 >:D
Indeed! US$11.10 for the cheapest variant, and US$24.70 for the full rated part!

Besides the military, there must be a few audiophiles which also crave this part.
 

Offline imo

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Re: LM723 die pictures
« Reply #81 on: March 09, 2020, 06:08:48 pm »
That price is not because the 723 chip is great, but because the package (metal TO-100) is not a mainstream anymore. It could be they bond manually 1000pcs from time to time on a machine gathering dust in TI's cellar  :D
PS: I would say the above chip is the oldest design, the artwork done manually into the rubylith foil.
All the others Noopy has analyzed are newer one done with CADs, imho.
« Last Edit: March 09, 2020, 06:16:11 pm by imo »
 

Offline SeanB

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Re: LM723 die pictures
« Reply #82 on: March 09, 2020, 06:54:46 pm »
More like they made a few hundred thousand, and ran them through the Aerospace qualification process, then took the remainder of the batch after test and placed them inside a controlled atmosphere storage facility, so that when they need a few hundred at some point, they have some already qualified, just needing another round of acceptance testing to verify them. Storage cost built into the price.
 

Offline imo

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Re: LM723 die pictures
« Reply #83 on: March 09, 2020, 07:08:28 pm »
..and placed them inside a controlled atmosphere storage facility,..
For example in Svalbard Global Seed Vault  :D
 

Offline TOTALCHIPS

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Re: LM723 die pictures
« Reply #84 on: March 16, 2020, 04:03:43 pm »
I recently found this component, the Fairchild Mil version. Just to add to your collection.
 
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Offline Noopy

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Re: LM723 die pictures
« Reply #85 on: March 16, 2020, 04:22:57 pm »
Thanks a lot!
I will upload it soon!

Interesting, it´s not very different to the "normal" Fairchild LM723 but has some minor distinctions. Have to check that.

Thank!  :)
 
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Offline Noopy

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Re: LM723 die pictures
« Reply #86 on: March 16, 2020, 09:51:05 pm »
The JM38510/102 is online: https://www.richis-lab.de/LM723_08.htm

It seems that the design is not really different to the UA723: https://www.richis-lab.de/LM723_06.htm

Only the big transistor in the right lower corner is not connected in the UA723.
But it is no additional transistor. The UA723 has a smaller transistor placed a little bit higher that does the same job. I don´t know why they changed the transistor size...  :-//

The JM38510/102 is newer but seems to have the older design. Perhaps it was sold for a longer time because it has the MIL-spec.

Offline magic

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Re: LM723 die pictures
« Reply #87 on: March 17, 2020, 06:36:59 am »
This "transistor" is the zener of course, where is the collector? ;)
 

Offline Noopy

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Re: LM723 die pictures
« Reply #88 on: March 17, 2020, 08:31:04 am »
This "transistor" is the zener of course, where is the collector? ;)



The collector is green.  :)
OK, it´s not used as a tansistor but basically it is a Transistor.


...I´m still not so familiar with the LM723-topology. Is this part the Vref-Zener?
« Last Edit: March 17, 2020, 08:33:29 am by Noopy »
 

Offline magic

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Re: LM723 die pictures
« Reply #89 on: March 17, 2020, 10:35:20 am »
Yes.  And the pad it's connected to is VREF output.
 
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Offline Noopy

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Re: LM723 die pictures
« Reply #90 on: March 17, 2020, 10:42:05 am »
I thought so, thanks!  :-+

So they changed the size of the zener reference but kept the old one on the die... Interesting... Hm...  :wtf:

Offline Noopy

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Re: LM723 die pictures
« Reply #91 on: December 29, 2020, 04:04:44 pm »


I have a new LM723! Do you know RIZ, Radioindustrie Zagreb?  ;D They have built the IL72723.
The ceramic package is shifted a bit.  :o




Nice! Nothing special. But there is a failed bond.
You can see that the two parallel power transistors are somehow similar to the Tesla MAA723:
https://www.richis-lab.de/LM723_04.htm
Well both are soviet parts.


More pictures here: https://www.richis-lab.de/LM723_09.htm



I also have updated the Fake ST LM723CN:
https://www.richis-lab.de/LM723_00.htm
Nothing special, I just updated the text.
I´m pretty sure that´s a soviet design because of the particular transistor design.



I also have updated the Fairchild MIL-723:
https://www.richis-lab.de/LM723_08.htm




I was curious about the small difference to the "normal" Fairchild µA723 in the bottom right corner.




In the MIL-723 the Q6 and the D2 have their own collector area. In the µA723 they share the same collector area. D2 is a transistor working in breakdown as a zener reference.
Electrically that should make no difference but there could be a thermal effect. If Q6 gets hotter it conducts more current and so there is less current flowing through D2. Less current gives less voltage but with the higher temperature the zener voltage goes up. Perhaps both effects cancel themself at least partly. And of course better thermal coupling gives better compensation.  :-+


 :-/O

Offline Wimberleytech

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Re: LM723 die pictures
« Reply #92 on: December 29, 2020, 04:29:47 pm »
Great work Noopy.

I was talking to a good friend of mine about the 723.  He designed TIs first knock off of the 723 back in the early 70s.  It was news to me...he had never told me that--or I forgot!

I will see him next month on his ranch...will archive this thread to an iPad so we can discuss (no internet at his ranch).

 

Offline Noopy

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Re: LM723 die pictures
« Reply #93 on: December 29, 2020, 04:40:59 pm »
Thanks!  :)

That sounds interesting!  :-+

Offline Noopy

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Re: LM723 die pictures
« Reply #94 on: January 19, 2021, 07:34:01 pm »
Sorry, I posted a UA723-update in the wrong thread...  :palm:

Here you can find news about the UA723:
https://www.eevblog.com/forum/projects/voltage-regulators-die-pictures/msg3421856/#msg3421856
https://www.richis-lab.de/LM723_06.htm




 ;D 8)
 
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Offline imo

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Re: LM723 die pictures
« Reply #95 on: January 20, 2021, 09:42:35 am »
I like your on-chip current measurement based on the emitted light intensity :)

 
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Offline David Hess

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Re: LM723 die pictures
« Reply #96 on: January 22, 2021, 06:17:38 pm »
I like your on-chip current measurement based on the emitted light intensity :)

I remember seeing a table once for fusing capability for different bond wire diameters which could be used to make estimates for the minimum current which had been present to destroy a part.
 

Offline TOTALCHIPS

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Re: LM723 die pictures
« Reply #97 on: June 15, 2021, 03:16:00 pm »
An original LM723CN from ST Microelectronics.
 
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Offline Noopy

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Re: LM723 die pictures
« Reply #98 on: June 16, 2021, 03:28:21 am »
An original LM723CN from ST Microelectronics.

Interesting! I have a original ST LM723CN in the queue too. It looks a bit different. Coming soon...
Would it be ok for you if I put this picture on my website?

Offline magic

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Re: LM723 die pictures
« Reply #99 on: June 16, 2021, 08:37:09 am »
For old, pre-merger SGS product you could look for L123. It seems to be a 723 clone.
 
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Offline TOTALCHIPS

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Re: LM723 die pictures
« Reply #100 on: June 21, 2021, 12:20:10 pm »
Hi Noopy, Yes, you can use the photos I posted on your website.

Best regards.
 
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