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  • TI Thinks Resolved

OPA541: Phase reversal

art Number: OPA541

I'm using the OPA541 as a follower using a single supply,

I have a case during startup where the input is taken to the GND rail. However, the output shoots up to the positive rail. I'm assuming this is because of phase reversal.

I added diodes and a resistor to fix this, and it does somewhat. When the input goes to the GND rail the output at least goes down, although not all the way to the GND rail.

I've included some circuits and traces.

Do you any further guidance as to a protection circuit to use or other things that might happening with the part?

OPA541_PhaseReversal-201712292033.pdf

  • Hello,

    You are exactly right, what you are seeing is a phase reversal on the output due to exceeding the lower common-mode input limitation. Because the output can only swing about 3V (typical) from the supplies, in a single supply configuration you can't drive the output any lower than around 3V. Adding the diodes and resistor will prevent the phase reversal by keeping the device within its common-mode limitations, but the output will still be saturated and if you want the output to swing to ground then you will have to add a negative supply.

    Regards,

    Zak Kaye
    Precision Amplifiers Applications 

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