[sdiy] Opamp as a comparator

[John Speth]

Hi list-

I'm working on a quantizer project that uses a comparator.   I started the
design using an LM311 hoping to exploit the OC output for driving 5V logic.
I quickly found out that a 0-5V output swing results in an asymmetrical
hysteresis.  Now it's a plain old +/-15V comparator with positive feedback
for hysteresis.  I might as well have used an opamp as a comparator to save
the trouble of a pull up at the output.

My questions are: Are suitably fast opamps just as effective as purpose
built comparators in comparator applications?  How do I determine if an
opamp is fast enough for my application?

John Speth
mailto:johns at molectron.com 
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