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LM7322-Q1: Oscillation

Part Number: LM7322-Q1
Other Parts Discussed in Thread: LM7322, TLV9362


After applied LM7322 instead of TLV9362, oscillation occurs. We did not observe the symptom with TLV9362.

It's voltage control(inverted voltage) to switch FET gate, and has various bypass capacitors on power amplifier.

After applied a series resistor between gate of power amplifier and output of LM7322 to prevent, the symptom is solved.

If correct, could you let me know how to calculate value for resistor?



  • Hey JS, 

    Welcome to e2e! Thanks for posting! 

    I imagine you are implementing a circuitry similar to the Voltage-to-current (V-I) converter circuit with MOSFET

    I am curious about this: 

    has various bypass capacitors on power amplifier.

    Can I see a schematic (just the op amp portion)?

    The resistor you have introduced helps isolate the amplifier from the capacitive load of the FET gate. We have an existing TIPL training on Stability: The fifth video in Stability explains the RISO method under "Capacitive Loads

    I think I might have misinterpreted, can you please confirm that you are seeing oscillation with the LM7322 and not the TLV9362? I would expect it to be backwards. Since the LM7322 is a "Capacitive Load Tolerance Unlimited " while the TLV9362 is not "unlimited" cap load drive. Could you please also confirm power supplies and input signal voltage range and frequency? 

    All the best,