does comparator depends on current?

Thread Starter


Joined Sep 19, 2012

initially there was one preset for each IR sensor. I am making two IR sensors on a single board and i want to use only one preset. The current to the input terminals of comparators will obviously decrease. does it affect my circuit? i know that op-amps have very high input impedance so very little current flows into them, but still i don't want to take any risk by making a circuit without consulting people on this forum.


Joined Jan 10, 2012
An Op-amp can be used as a comparator, and is often used that way. However, you can run into problems for rapidly changing signals, as op-amps are slow, comparatively speaking. As long as your opamp has sufficient bandwidth and slew rate for your signal, you are OK. If not, then use a faster comparator.


Joined Jul 18, 2012
A comparator uses a very fast output stage that can recover from saturation quickly. An op amp uses a linear output stage, and the designer doesn't worry about recovery from saturation because it is assumed that op amps aren't used in the saturated mode. Aside saturation recovery op amps function fine as comparators as long as speed isn't a concern. An LM324 from TI might recover is 300Ns while one from a competitor might recover in 3 Us. This means that op amps don't function well as high speed comparators, but they are fine in low speed applications like sensing switch closures, IR sensing in the Us range, and other mechanical tasks. PS- I wouldn't put a lot of faith in SLOA67 from TI.