Op amp comparator circuits – Inverting and non inverting

Op amps and comparators are always comparing the voltages at the inverting input and the non inverting input. The voltages at the input affect the output.

Without feed back (letting the output voltage influence one or both inputs) you have a comparator circuit.

LM358 op amp wired as non inv and inverting comparator circuit learning electronics lesson 0020
LM358 op amp wired as non inv and inverting comparator circuit learning electronics lesson 0020

Basic rules are….

  • Non inverting input with a higher voltage than the inverting input = a high output.
  • Non inverting input with a lower voltage than the inverting input = a low output
  • Inputs just look at voltage. They don’t let current (other than a small amount of leakage) through them.
  • High output means the output voltage is as close to the positive supply voltage as the output can provide, up to the maximum current that it can provide.
  • Low output means that the output voltage is as close to the negative supply/ground voltage as it can provide, up to the maximum current that it can provide.

To support this site, check out the following links:

Home page

  • Information on this site is not guaranteed to be accurate. Always consult the manufacturer info/datasheet of parts you use. Research the proper safety precautions for everything you do.
  • Electronzap is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com.