[sdiy] Comparator = Opamp ??

[jh.]

> A comparator is a digital device that outputs a 'high' signal (logic 1 or
about 4 to 5 Volts), when the voltage on the + connector is higher than the
voltage on the - connector. If the one on the + is lower, it outputs a 'low'
signal (logic 0 or 0 Volts).
>
> An Opamp has exactly the same appearance in schematics, though i get the
impression (from Circuit Maker 2000 (simulation software)) that it behaves
differently. Can anyone tell me the difference, or state that they infact
ARE the same...


Things have evolved quite a bit since the start, so you have a lot of very
specialized
devices, both for opamps and comparators. But in the beginning, a comparator
was just an opamp without the compensation capacitor - no dominant pole, no
closed loop stability, but much faster than an opamp.

I think I've seen one circuit from Electro Harmonix (the masters of cheap
design, in any positive sense of the word), where one comparator of a
quad package is abused as a linear opamp - quite some feedback network to
get
it stable, but avoids an extra DIL package for opamps when one comparator
was unused. Not that such things would be wise nowadays when capacitors
are more expensive than opamps ...

JH.