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UA741: Abnormal output voltage behavior

Genius 4165 points
Part Number: UA741

Hi,

My customer is using UA741 as a 25 times non-inverting amplifier with AC coupled input.

But  they found some parts had an abnormal behavior like the waveform in attached PDF file as  "NG part".

(The output voltage is clipped to the negative rail)

UA741 Waveform.pdf

I can’t share circuit schematic on this thread because it's confidential, but I'll be able to share via e-mail or private message if you need.

Any advice will be very appreciated.

Thanks,

Go

  • Hello Go-san

    How many samples had the abnormal waveform?  The abnormal waveform looks like the op amp is broken or there is an open solder joint on the PCB. I suspect broken because an open solder joint is unlikely to distort the input signal. Does the input signal originate on the circuit board or does it come from a connector?

  • Hi, Ron-san

    Thank you for your comment!

    We heard that customer got 2 parts with abnormal waveform.

    and attached waveforms are acquired in our lab with using abnormal sample and normal sample sent form customer.

    we used pulse generator for input signal when we took this waveform.

    If you have any other question, please let me know.

    Thanks,

    Go 

  • Go-san,

    Is lab setup like this?

    If input is AC coupled then R3 must be used.  All inputs need a DC operating point.

    If input is direct, then there must be a short that distorts the input waveform. 

  • Ron-san,

    Yes, Customer has placed R3.

    Can I send you the detailed information(resistor value and other components value) by private message?

    Thanks, 

    Go

  • Go-san

    Yes, you may. 

    Note that op amp signals that go to a connector may cause ESD or EOS damage to the op amp.