A matter of preference? Op amp feedback loop schematic

1

The circuits below differ in one aspect. The op-amp to the right/bottom either has a feedback loop via the inverting input or the non inverting input and the signals fed to it are swapped. In other words, the + and - input are swapped. Both circuits produce the same output.

What they do is subtract the voltage made using the potentiometer to the left from the AC input thus shifting the mean of that input signal above or below 0 Volts.

Assuming I have not made any mistakes in my simulations, are there any reasons to prefer the one approach above the other?

neg-20210314-1215
neg-20210314-1215924×628 25.1 KB

pos-20210314-1213
pos-20210314-12131116×628 23.9 KB

2

It surprises me to learn the positive feedback version works. Have you tried it in hardware? I wonder if it’s stable.

The negative feedback version is a standard op amp differential amplifier. If only because it and not the other is the way everyone shows to do it, I’d use that.

2 Likes
3

In the simulation in works, also to my surprise.