Help on op-amp (?) circuit

[Frederic Breitwieser]

> So what's the difference between the 2 devices, I have never understood this.
> You can use an op amp for a comparator but not visa versa ?

The 339 is a dedicated comparer Op-Amp, its designed specifically for
switching its output at a certain threshold from 0 to 1 or 1 to 0
depending on how wired... where as the LM334 has an analog swing for an
output... and you'd have to buffer its output with a TTL gate or two to
interface to 74xx chips, or a CMOS gate for microprocessors.

I had recommended the 334 because radio shack has them in stock, and
while its not my favorite store, they don't have a minimum order :)