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Original question:

OPA838: unstable voltage follower in TINA - TI 25 MHz Squarewave

OPA863: Unstabel simulation results - Current flows into to INPUT of IC

Lukas Maier
Prodigy 20 points
Part Number: OPA863


Tool/software:

I have been trying to simulate a simple voltage follower with the OPA863-IC.

I get a strange behavior which I can't explain to myself.

There is a lot of current flowing into the noninverting Input of the amplifier.

Also, the output shape doesn’t look right.

7026.follower_only.TSC

  • 0
    TI__Genius 16855 points

    Hi Lukas,

    It does seem like the model is having trouble clamping the internal nodes accordingly as the device starts slewing. If you slow the edge rate of the input signal both the input current and output seem to behave appropriately. Due to the model architecture, internal clamps control the behavior and often times with fast signals it causes some glitches as it does not clamp fast enough. I do not believe this is something you will see in real silicon as it will just hit its slew rate limit. 

    Best Regards,

    Ignacio