uA723 voltage regulator viable in 21st century?

[glarsson]

Yes. They were included in the ellipsis.

It is weird that the components I used when I  started with electronics, ca 1975, are still manufactured and used in new designs.

[Wolfgang]

Isn't LM723 the same part as UA723? 
Aren't those just the new (TI) and old (National) part numbers for the same product?
Was LM723 some sort of TI "remake"(?) of the original National uA723?

I have a box of all kinds of 723s at home, from different manufacturers. I have some from
- National Semiconductor with LM Prefix
- Fairchild with uA Prefix
- SGS ATES with SG prefix
- ST with LM prefix
- RCA with CA prefix
- Harris with CA prefix
- Texas Instruments, some with LM and some with uA
- Siemens with TDB prefix
- Tesla with MAA prefix

- plus some more exotic stuff where I could not derive the manufacturer.

 I simply dont know which ones were
- just relabellled
- built as a second source in a chip factory owned by the company
- cloned

In the last years, the major producers were National, ST and TI.
The spec sheet look almost identical among all 723 manufacturers.

Hope that helps. As said, I hope these chips wont survive me.

[iMo]

FYI - Tesla company produced "hybrid" ICs with the 723 die. Interesting to see how they mimicked the 723's function in the negative rail with discrete components - here is a +/-15V linear voltage regulator (in metal DIL24 package, you may click on the hybrid IC in the mid text):
http://www.mlab.cz/Articles/PodKapotou/HybridIC_WSH913/DOC/HTML/HybridniObvody_WSH913.cs.html

[Wolfgang]

FYI - Tesla company produced "hybrid" ICs with the 723 die. Interesting to see how they mimicked the 723's function in the negative rail with discrete components - here is a +/-15V linear voltage regulator (in metal DIL24 package, you may click on the hybrid IC in the mid text):
http://www.mlab.cz/Articles/PodKapotou/HybridIC_WSH913/DOC/HTML/HybridniObvody_WSH913.cs.html

Cool ! I never saw  one of those ! Highly exotic, but why not !

[Alex Nikitin]

FYI - Tesla company produced "hybrid" ICs with the 723 die. Interesting to see how they mimicked the 723's function in the negative rail with discrete components - here is a +/-15V linear voltage regulator (in metal DIL24 package, you may click on the hybrid IC in the mid text):
http://www.mlab.cz/Articles/PodKapotou/HybridIC_WSH913/DOC/HTML/HybridniObvody_WSH913.cs.html

Note: there is at least one error in the schematics on that web page, top end of R12 goes to pin 22, not to pin 19.

Cheers

Alex

[bd139]

FYI - Tesla company produced "hybrid" ICs with the 723 die. Interesting to see how they mimicked the 723's function in the negative rail with discrete components - here is a +/-15V linear voltage regulator (in metal DIL24 package, you may click on the hybrid IC in the mid text):
http://www.mlab.cz/Articles/PodKapotou/HybridIC_WSH913/DOC/HTML/HybridniObvody_WSH913.cs.html

Cool ! I never saw  one of those ! Highly exotic, but why not !

Yes very interesting indeed.

I really like looking at some of Tesla's old stuff, and most of Eastern Bloc tech. It was amazing progress for the times and I have nothing but respect for the engineers. Thanks to COCOM etc it wasn't easy but they did good.

Also their DIP packages were 2.5mm not 2.54mm which makes much more sense for us metric lot!

[iMo]

The Tesla's pitch was 2.54mm with all the DIL/DIP ICs they ever produced.. http://www.tesla-ic.com/cat/

[bd139]

Who produced 2.5mm then?

[iMo]

Soviets.. And "VEB Kombinates" in East Germany..
Usually with larger packages. The smaller one (DIL14-16) were all 2.54mm, afaik.

PS: I've spent a while browsing the beautiful site https://zeptobars.com/en/
but no 723 die-shot there, a pity..

[not1xor1]

FYI - Tesla company produced "hybrid" ICs with the 723 die. Interesting to see how they mimicked the 723's function in the negative rail with discrete components - here is a +/-15V linear voltage regulator (in metal DIL24 package, you may click on the hybrid IC in the mid text):
http://www.mlab.cz/Articles/PodKapotou/HybridIC_WSH913/DOC/HTML/HybridniObvody_WSH913.cs.html

Note: there is at least one error in the schematics on that web page, top end of R12 goes to pin 22, not to pin 19.

Cheers

Alex

Yes, the positive rail is the master and the negative "slave" is just inverting the positive output.
I wonder if that might cause any problem when the master BJT limiter switches on as negative rail BJTs might get reverse biased in case of short on the positive one.

[iMo]

Here is a model of the WSH913 Negative rail:
1. it gives -14.99V/-50mA out (-14.97V/-75mA),
2. max current -87mA with shorted output.

With positive rail=0V you get:
1. max -12..-13mV out (for 100-300ohm load) and
2. max -70mA with shorted output.

PS: the negative output voltage is referenced by the positive rail voltage. The 723's Vref plays almost no role with the negative rail voltage level here (ie. with 723's Vref= 6..10V you get the same output voltage)..

PPS: below the mod - now the negative output is referenced by the 723's Vref. Otherwise it works the same, except it does not sense a short on the positive rail.

[not1xor1]

Here is a model of the WSH913 Negative rail:
1. it gives -14.99V/-50mA out (-14.97V/-75mA),
2. max current -87mA with shorted output.
...

well but if the positive rail output is brought to 0V by a sudden short, then Q6 emitter is connected to -15V of the charged output capacitor (just for a short time) while the base of the Q5-Q6 darlington is a bit above 0V (Q2 is saturated).
Given just 15V of output voltage it is unlikely that the voltage gets above Q5+Q6 Vbe breakdown.
Anyway, since somebody might be tempted to use this design for higher voltages, I think it might be useful to remark the need for a reverse bias protection diode.

[orolo]

Soviets.. And "VEB Kombinates" in East Germany..
Usually with larger packages. The smaller one (DIL14-16) were all 2.54mm, afaik.

PS: I've spent a while browsing the beautiful site https://zeptobars.com/en/
but no 723 die-shot there, a pity..

I've been decapping some suspect (beta > 400) BD139s from ebay lately and figured it couldn't hurt to throw some 723s into the acid pot. My microscope is barely good enough for discretes, so please excuse the Frankenstein composition.

The chip is a genuine, very old, uA723 from TI, marked: TI LOGO,  2020Z7T  UA723CN. Images attached below.

I've also decapped a very suspect NS LM723 from ebay, but the acid was quite diluted, and the quality of the images is much poorer. I can upload it, if someone is interested.

[Wolfgang]

Hi,

I am curious about the other NS723 as well. Which acid did you use ?

Wolfgang

[iMo]

It seems the MAA723 is of a simpler design. And the Vref noisier than the original, imo. Below the die-shot from the above .cz link.

[orolo]

I am curious about the other NS723 as well. Which acid did you use ?

Hi. Some time ago I opened a thread about decapping, and BarsMonster helped me to refine the technique. Essentially, I use 98% sulfuric acid very carefully heated in a test tube. The tube is held in a fixed rig, with a perforated stopper degassing into an alkaline solution, with a buffer in between to avoid catastrophic reflow of the solution into the acid when cooling.

I'll post the NS723 later. It's a lot uglier, though  .

Edit: NS chip attached below. With direct light at low mag. it looks nice, at higher magnification didn't manage to capture much detail. At least I can see the NS logo, a copyright symbol, something like UK, and 723D below. I guess the chip is legit, if maybe a reject.

BTW, in all the examples there seems to be a big diode next to the output stage, connected to a pin. Could it be the zener pin?

[iMo]

That is the output zener. Not connected in MAA723 (metal package).

[orolo]

I agree, that one is easy. Following the same schematic, do you think the Zener D1 is where I put it? I'm not sure at all about R2, D1 and Q1. As a real addict to silicon porn, I watch all the pics, but know nothing of the real thing.

[iMo]

The Vref zener is the D2, afaik.. 
PS: the internal schematics from 1968 differs from TI's latest.. Most probably the vendors did changes in the original design..
PPS: I think there is a bug in TI's schematics - the D2's anode should not be grounded..

[iMo]

I agree, that one is easy. Following the same schematic, do you think the Zener D1 is where I put it? I'm not sure at all about R2, D1 and Q1.

It seems it matches the '68 schematics well..

[orolo]

I like the 723 for the low noise. I doubt the comercial versions use buried zeners, because a discrete buried zener as the LM329 is about 90 cents a piece, last time I bought them. It would be great checking where the D2 zener is in the dies, but it seems hard to find. D3 stands out, and D1 is connected to V+, which is easy to locate and follow.

Anyway, IMO the NS die seems easier to understand. The current limit transistor Q16 is in the upper left corner, the differential amp Q11-12 at the middle of the left side, Q13 at the lower left corner,  and I think D1 and D3 are rather easy to place. Placing D2 should be easy, since the Vref pad must be the one at the bottom left, but I get lost in all the things happening in at the center of the die. I really hope there isn't a bandgap circuit there.

[m3vuv]

its funny but the infinion sg1532 is still available on ebay but quite expensive,i just brought one,but looking for a good schematic to build a 3-30volt 30 amp psu,may use one for a 723 with mods.

[Terry Bites]

Well people like thier comfort zone and IC names they can remember. I've never used a 723 becaue the're are better components. Of you can afford lundahl transformers then your not building down to a cost, go luxury. My pet hate is the 555! I dont see what its good for except flashing LEDs and making crap monostables. Its a teaching aid but jack of all trades but master of none. Put them in the crusher with the 741s!
Sorry guys....

[David Hess]

Well people like thier comfort zone and IC names they can remember. I've never used a 723 becaue the're are better components.

But those better components are either less versatile than the 723 or much more expensive.  For instance the inexpensive regulators which commonly replace the 723 do not support a current limit below their design current without external circuitry.

My pet hate is the 555! I dont see what its good for except flashing LEDs and making crap monostables. Its a teaching aid but jack of all trades but master of none. Put them in the crusher with the 741s!

I do not like the 555 either, but as I became a better designer, I found more virtue in older parts like the 301A operational amplifier because they could do things that newer but easier to use parts could not.  The 301A for instance has a common mode range which includes the positive supply, and external compensation allows for clamping and higher performance.

[Wolfgang]

Well people like thier comfort zone and IC names they can remember. I've never used a 723 becaue the're are better components.

But those better components are either less versatile than the 723 or much more expensive.  For instance the inexpensive regulators which commonly replace the 723 do not support a current limit below their design current without external circuitry.

My pet hate is the 555! I dont see what its good for except flashing LEDs and making crap monostables. Its a teaching aid but jack of all trades but master of none. Put them in the crusher with the 741s!

I do not like the 555 either, but as I became a better designer, I found more virtue in older parts like the 301A operational amplifier because they could do things that newer but easier to use parts could not.  The 301A for instance has a common mode range which includes the positive supply, and external compensation allows for clamping and higher performance.

The discussions about 723 obsolescence have the tendency to repeat themselves. Fact is that
there is no equivalent or better part for the range of specs (40V, 150mA, ...). There *are* better parts for less voltage and current, but thats like apples and oranges. The reason why it still sold after 50 years is that there is *no* direct replacement, obviously.