op amp voltage follower stability

Thread Starter

MikeJacobs

Joined Dec 7, 2019
162
Hello

I have a need for a simple voltage follower
However, i know it is not as easy in practice as in a text book.
Text book simply shows no resistor and tieing the output back to the inverting terminal
I understand this is not proper.

What is the proper way?
 

OBW0549

Joined Mar 2, 2015
3,546
Text book simply shows no resistor and tieing the output back to the inverting terminal
I understand this is not proper.
Long ago, back in the days when op amps had large input bias currents (many nanoamps or even several microamps), it was often necessary to balance the impedances seen by the two op amp inputs so that the bias current wouldn't generate an input offset voltage. Hence that resistor (I assume) you were expecting between the op amp's output and its inverting input.

But modern op amps usually have such small input bias currents that extra resistor is no longer necessary. That is why your textbook doesn't show one in the circuit.
 

Thread Starter

MikeJacobs

Joined Dec 7, 2019
162
Just everytime i make a following without a resistor on the feedback and a cap in parallel someone yells at me and says its unstable. I never understood why but just did it
 
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