I have an OP484 opamp and was thinking about using it with positive feedback and use it as a comparator. To limit stress I could just use resistors to limit current. But My question is if using a an Op-Amp as a comparator is a good idea. I know I read somewhere before of an application note talking about pros and cons of using an op-amp as a comparator.
Can anyone help clarify? or any possible problems/issues/limitations that I should be aware of? and if they know that application note I am talking about, can you help me find it.
Thanks Rick, this is a great resource. So, it seems to me that in summation, don't use an op-amp as a comparator, even though sometimes it is tempting economically. Interesting, thanks again!
The analog devices article makes good points both pro and con.
Op amps can be used as "sloppy" comparators in some applications.
Often, the slow speed of the op amp, in addition to hysteresis, is an advanatge.
One common application are clip/signal present indicators used in pro audio equipment.
Before chosing an op amp as a comparator, check to make sure that there are not back-to-back protection diodes across the differential inputs.
These diodes limit certain op amps in applications other than comparators as well e.g. peak detectors, DC clamps etc.
Some common audio op amps that do have diodes - and cannot be used - are the NE5532, NE5534, LM4562, LME49710, 720 and 740.
Common audio op amps that do not have protection diodes - and can be used - are the 4556, MC33078, TL071, 72 and 74.
Unfortunately the OP484 has protection diodes. If you look at the simplified schematic you will see clamp diodes QL1 and QL2.