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LM321: LM321MF/NOPB op amp heating issue

Alon Chen
Intellectual 425 points
Part Number: LM321

Tool/software:

Hi Team,
As shown below, a customer's PWM is connected to the positive input of an LM321. When the MCU is not initialized, the PWM input signal level is uncertain. This caused some op amps to overheat, while others from the same batch did not. Furthermore, the overheating disappears when the PWM level changes. What could be the cause? Please help analyze this. Thank you.

  • 0
    Guru 317280 points

    With capacitors connected directly to the output, this opamp is likely to be unstable and to oscillate.

    What is the purpose of C20/C11? If you want a smooth output signal, just filter the input signal, or put a resistor between the opamp's output and the capacitors.