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LM358: output abnormal

David Yang
Intellectual 740 points
Part Number: LM358

Tool/software:

Hi,

This is a mass-produced case, with the same PCB and surrounding parts in the same conditions.

The output waveform appears as follows, causing the output to be abnormal.

Is this phenomenon related to the IC? If not, do you have any suggestions?

Thanks & best regards,

  • 0
    TI__Guru* 77521 points

    Hi David, 

    David Yang said:
    Is this phenomenon related to the IC? If not, do you have any suggestions?

    Where is the LM358 is located? Is it located at U431-B op amp. Two op amps configuration is totally separate. U431-B has its localized feedback; and the power amplifier is driving the output load on its own and has its own feedback.  

    The power amplifier on the right has stability issues (red rectangular box). It is likely driving capacitive load and requires loop compensation in order to get rid of the osicllation issues. So the issues are the Power Amplifier's feedback loop in this case, where the compensation loop does not adequate phase margin. 

    If you have other questions, please let me know. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    TI__Guru* 77521 points

    Hi David, 

    I am going to close this query, since I have not heard from you. 

    If you have other questions, please let us know. 

    Best,

    Raymond

    HVA Application Team