OP-AMP and voltage comparator

[Lucifre]

I know it may seem like a stupid question, but what is the difference between OP-AMP and a voltage comparator? they have the same symbols. also if anyone could provide me with some links to sites about voltage comparators.

 

[ppenday]

opamp will have negative feedback and comparator will have positive feedback.

 

[mists]

in general, opamp operate in close-loop, and comparator operate in open-loop.

 

[huojinsi]

As mists's mentioned, the OP AMP generally operates in linear region and the relation of input and output is a closed loop. in contrast the comparator operates in nonlinear region and the relation of input and output is a open loop.

 

[tlihu]

Linearity is important for Op-Amps while comparators do not care about the distortion of outputs.

 

[Kral]

Lucifre,
Op Amps are designed to be stable under open loop and closed loop (with negative feedback) applications. Comparators are not necessarily stable open loop, and are almost never stable with negative feedback. Comparators are designed for high slew rates. Stability is compromised for speed. Positive feedback is often used to prevent the comparator from staying in its linear region, as well as for providing hysteresis for noise imunity. In addition, comparators frequently have open drain or open collector outputs, which allows for a variety of load pull-up voltages. The open drain/collector also allows you to "Nor" the outputs by simply connecting them together. In some applications, an Op Amp can be used as a comparator. Disadvantages are:
~ You are stuck with the active outputs.
~ Slow switching speed.
regards,
Kral

 

[on1aag]

Opamp's are (generally) used in linear applications where
(generally) negative feedback is applied. Comparator's
are intended to be used in non-linear applications where
(generally) no feedback is applied. They are optimized for
switching applications and will recover faster from overdrive
situations. The output stage is also very different, some
have output stages that swing from 0 Volts to something
between three to five volts while other's have an open
collector output that can swing from 0 volts to the applied
voltage at the collector resistor. The first category is
intended to drive (TTL)logic circuits, while the second
category can be used to drive a large variety of loads like
leds, small light bulbs and even solenoids.
Note that comparator's (generally) have a ground connection.