op-amp pin Identification

[fixr1984]

I came across this schematic for a 3 band tone control and cant seem to figure out
what the ic pin nimbers are. It looks to me that they are using two single op-amps.
Any help is apreciated.

http://www.montagar.com/~patj/3btone.gif

[Mark Hammer]

Tiny, eh?  Here's a useful tip.  If you see one pin tied directly to ground (or Vb), then that op-amp is being used in inverting mode.  In this instance, the input and output stage are both inverting, which means the output is in phase with the input.

What pin is that, you ask?  If it is a single 8-pin op-amp, then the pin going to ground is the + pin, which will make it pin 3.  If one uses a standard 8-pin dual op-amp, then the + pins will be 3 and 5.

BTW, that input stage is a little incomplete.

[fixr1984]

Thanks for the info. I was guessing ground was 3. Would that make 2 and 6 tied
together thru R1?
How incomplete are we talking here?

[Mark Hammer]

It's incomplete in the sense that it is essentially a sub-circuit for insertion into an existing path, rather than a stand-alone circuit.

[fixr1984]

Gotcha, actually I was going to use it in an existing circuit so it sounds like it
should work out.

Thanks