# Dumb question about circuits with diodes

## Main Question or Discussion Point

I'm at a loss as to how there is an output voltage for this circuit when I think the diode is facing in the wrong direction. Or is it possible to get an output voltage? Can someone help me analyze it. Just assume resistance is R and current through resistor is I and voltage drop accross diode is 0.6 V. Thank you!!!

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## Answers and Replies

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berkeman
Mentor
The diodes are just clamps to be sure that the output does not go above the + rail or below ground. The rest of the amp circuit makes no sense, unless it represents some fixed gain (unity gain?) amplifier. If you do not connect feedback on an opamp circuit, the output will indeed peg.

the rest of the amp circuit makes no sense
This kind of circuit is called comparator. The opamp will trigger when voltage over variable resistor will be equal to the input voltage -> making the opamp go into saturation i.e to ~+Vc, assuming that Vo should be less than Vc, those clamps makes sense.