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OPA124: OPA124 - changes between different delivery lots

Christoph von Thuelen
Prodigy 30 points

Part Number: OPA124

Hi all,

 

i am looking for additional information on changes between different delivery lots.

In the past (appr. 4 years ago) some amplifier board with the OPA124UA, top marking (3rd line) "08CL66" have been manufactured and they performed very well.

 

The last devices i received appr. 2 weeks ago (OPA124UA, Top marking (3rd line) "68CXT6") show spurious oscillation on the same PCB with complete unmodified environmental conditions.

This means:

- replaced OPA124UA "08CL66" (old one) by "68CXT6" (new one)

- same power supply

- same stimulation with same source

- same cableling

- same oscilloscope probes

 

Q1: Can you provide me with informations on changes or differences between these two OpAmp versions names above?

Q2: Can you decrypt the top marking code (3rd line) of both devices named above (e.g. production date, fab, revision etc.)?

 

Thanks in advance.

 

Regards,

Christoph

  • 0
    TI__Guru* 93105 points

    Hello Christoph,

    We don't fully disclose our marking code because it would allow IC counterfeiters information that they could use. An incorrect code can be an immediate clue that a device has been counterfeited.

    I can tell you that the older OPA124UA devices you were using were manufactured in 2000, while the newer ones were manufactured in 2016. During that time the OPA124UA wafer processing underwent a major fab move from one fab location to another. A major move can introduce some shifts in dc and ac electrical characteristic distributions. Despite that they must still meet all the datasheet specifications.

    Occasionally, when a device such as the OPA124UA undergoes a major fab change they can take on somewhat different dc and/or ac characteristics than they did before the move. Those parameter shifts can expose a marginal stability condition. I suspect that the 2016 devices have somewhat different gain/phase performance than the earlier ones and that has become a stability issue for your original design. If the original amplifier had just enough phase margin to where the circuit was marginally stable, the new op amp may have a little less phase margin and the circuit becomes unstable. Often, phase margin reduction comes about because of high capacitve loading on the op amp output, or input summing node.

    If you can provide us your OPA124UA circuit diagram, supplies, input signal information and output load conditions, we can take a look at it and assess the phase margin. There may be a relatively simple solution that could be employed to assure the circuit remains stable with any vintage of OPA124UA device.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • 0 in reply to Thomas Kuehl
    Prodigy 30 points

    Hello Thomas,

    thank you very much for your detailed answer.

    Providing circuit diagrams or other documents is no necessary at the moment.  I am in discussion with my customer about the test conditions (actual requirements and derived stimulation signals) and if we are testing to tough.

    So, if there is any support needed, i will come back to this discussion.

    Regards,

    Christoph

  • 0 in reply to Christoph von Thuelen
    TI__Guru* 93105 points

    Hello Christoph,

    Thank you for letting me know the status.

    Regards, Thomas

    Precision Amplifiers Applications Engineering