I'm examining the datasheet of the OPA192. When the inverting input of op amp tied up the op amp output and if the non-inverting input of op amp had been floating, what would have happened the op amp output.

Note: OPA configuration is like below (Voltage follower).

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I performed the simulation of OPA192 in LTSpice. If I connect a voltage source with a voltage value equal to or less than the supply voltage, I can see same voltage level with input because of voltage follower configuration. But If I leave floating of the op amp input pin, I don't have a meaningful outcome from simulation. Does the opamp output oscillate?


1 Answer 1


If a pin is left floating, the voltage on the pin can be any value between the supply voltage depending on the size of the leakage current.

To ensure the pin never floats when there is no input signal, tie a large resistance, say 100k, between in non-inverting input pin and ground, and the output will default to 0V, so its behaviour can be deterministic.

With regards to stability, since its an undefined voltage its not definitive to say what its behaviour should be. (In practice, I would believe this wouldn't affect the stability of the op-amp tied in this buffer configuration, given that its unity bandwidth is quite high, and generally leakages are quite slow.)


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