UA741: Offset pin not working

Roberto Bozzolo

Part Number: UA741
Other Parts Discussed in Thread: TLE2021, TL071, OPA277, OPA177, TL031

Tool/software:

Hello, we have bought a bunch of op-amps UA741CP from Mouser distributor and tried to use them in one of our typical data acquisition and control boards but have found the input offset pins are not working since we cannot compensate the input offset (actually the output is not changing at all by operating on R11 trimmer). We are testing it with R1 and R2 connected together, so zero volt input.

The offending parts are marked 48AELYM-G4

This is an abstract of the electrical drawing showing a typical circuit in which the op-amp is used (we are using this kind of circuit extensively in several boards of our production):

We have checked board circuitry and found nothing wrong, moreover using other 741s we have in our lab the offset circuit is correctly working on the very same board.

We have checked 10 out of 100 pieces bought and found all defective. This is an image of components not working correctly:

An example of 741 correctly working in the same board is marked differently (01AK7DM).

What can be the problem here? It seems this lot of components is not working correctly.

8 months ago

0 Clemens Ladisch 8 months ago

Guru 318490 points

Since PCN# 20230713001.1, this device uses a new die with a different architecture. This prevents the old offset adjustment method from working, so the offset pins are not connected on new devices.

The datasheet does not specify a minimum offset adjust amount, so I guess this is not considered a defect.

Similar devices in the PDIP package with better offset voltage are the TL071, OP07C, TLE2021, or OPA177/OPA277.

0 Raymond Zhang1 8 months ago

TI__Guru* 77541 points

Hi Roberto,

Roberto Bozzolo said:
This is an image of components not working correctly:

As Clemens indicated, the UA741 has gone through FAB changes recently and the Offset-Voltage Null feature has been removed or disabled.

https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/5485/PCN20230713001.1.pdf

The Vos performance should be better than the old offset specification, shown in the table below. That is likely the reason that the feature is being disabled.

There are other techniques to perform the Vos adjustment. If you need help, please let me know.

Best,

Raymond

0 Roberto Bozzolo 8 months ago in reply to Clemens Ladisch

Prodigy 10 points

Ok, good to know. Unfortunately this change is not reflected in product documentation which dates back to 2018.

I suppose we will go the TL071 way: it's an easy replacement which implies only the change of the offset trimmer value and we are already using it in other projects so we have it in our parts list.

Thanks for the info and the support.

0 Roberto Bozzolo 8 months ago in reply to Raymond Zhang1

Prodigy 10 points

Thanks for the info. I won't question on such a document I'm not familiar with, but I wonder where I would know of this change impact on device specs since I read (highlights are mine):

Anticipated impact on Form, Fit, Function, Quality or Reliability (positive / negative):
None

0 Raymond Zhang1 8 months ago in reply to Roberto Bozzolo

TI__Guru* 77541 points

Hi Roberto,

The follow TL071's offset pin is also removed due to the new FAB.

https://www.ti.com/lit/ds/symlink/tl071.pdf?ts=1743144842872&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTL071

In the modern op amp, these Vos feature is no longer needed because the process can consistently make low Vos op amp. The general purpose op amp typical has Vos (refer to input) > 1mV. If you want lower Vos op amp (<1mV), then you should consider our precision op amp, where you do not need to worry about the Vos issues or trimming the Vos.

https://www.ti.com/amplifier-circuit/op-amps/precision/overview.html

Roberto Bozzolo said:
Anticipated impact on Form, Fit, Function, Quality or Reliability (positive / negative):

The new FAB process has gone through performance verification, reliability testing, process variation, production correlation between old vs. new, qualification, certification process related compliance tests. This FAB development and changes take for years before it is finalized. So the impact on the reliability should remain unchanged. In most of the cases, the new FAB process reliability parameters have improved over the old FAB.

To the end user, the quality variables are a part of new FAB's verification and validation process. For instance, long-term stability, stress testing, manufacturing consistency, functional testing, mechanical & electrical interface etc. have well passed certification stage. The new RFAB began production in 2009. Many of these op amp product started to switch from old to new FAB in last few years.

If you have additional questions, please let us know.

Best,

Raymond

0 Roberto Bozzolo 8 months ago in reply to Raymond Zhang1

Prodigy 10 points

Wow! We will need to consider all that!

By the way, we are already using TL031 for some other application of ours: did this component too undergo a similar update?

0 Clemens Ladisch 8 months ago in reply to Roberto Bozzolo

Guru 318490 points

See the list in the PCN; it also applies to the TL031.

0 Raymond Zhang1 8 months ago in reply to Roberto Bozzolo

TI__Guru* 77541 points

Hi Roberto,

Yes, TL031 is on the affected list in the PCN.

https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/5485/PCN20230713001.1.pdf

If you have other questions, please let us know.

Best,

Raymond

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UA741: Offset pin not working