<use@[EMAIL PROTECTED]
> wrote in message
news:b8d97ea0-82c5-47ef-9784-a398bebb3aee@[EMAIL PROTECTED]
>
> In fact, some time ago I asked
> on this very newsgroup what is the difference between an op-amp
> and a comparator, and the replies that I received then where that they
> are basically the same thing, that comparators are "optimised for
> switching", so due to those idiots (as you put it) back then I have
> been
> missed informed till yesterday. Just goes to show how careful one
> needs to be about info posted here. In fact, what our designer wanted
> was a little hysteresis symbol inside the op-amp symbol, which is
> the agreed symbol for comparators with built in hysteresis (?).
> And the datasheet of this particular one, does show the
> correct symbol.
>
FYI:
Comparators really are opamps. There are two main differences I can think
of
right now. First, they don't have compensation to prevent oscillation, so
they are faster, but more likely to oscillate in some situations.
Secondly,
many if not most comparators are 'open collector', meaning they can only
sink current on the output, and not source it. This is useful in many
situations, but you need to be aware of it to design the circuit properly.
However, if you look on one of the mfgr's sites for information about
these,
they keep the comparators separate from the opamps. The usage, and thus
the
internal optimizations, are quite different. Comparators are always used
to
detect that a certain input voltage has exceeded some limit. Opamps, on
the
other hand, are used to perform some kind of calculation with the input
voltage, such as scaling, differentiating, integrating,
sample-and-holding,
etc.
I don't know about the symbol. See this:
http://encon.fke.utm.my/nikd/latest/sloa067.pdf
Regards,
Bob Monsen
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