Quick power supply and op amp question.

[mills]

Two really basic questions...

First, looking at the schematic here,

http://www.experimentalistsanonymous.com/diy/Schematics/ADSR%20Generators%20and%20Envelope%20Generators/Paia%202720-11%20Envelope%20Follower%20Trigger.gif

The op amps with a 100pf cap from pin 1 to pin 8... how do I figure out what I need them to be doing, or what an appropriate part number would be?  I'd love to just use a quad or two dual op amps, but if I need that compensation/whatever it actually is cap, I would guess I can't.  I'm not well versed enough in my options to know of possible op amps to use...

   -Bonus question... looking at the design, it shouldn't need much modification to run at +/-12V rather than +/-9V?  No special reason... just going trying to simplify power supplies on a board that this will be on.

Second, if I have +/- 12V, but was going to use only the +12V and ground in a pedal, can I just leave the -12V disconnected?  Or do I need to deal with it somehow (shunt it to ground through something?  I dunno... )

[Cliff Schecht]

You shouldn't have any problems with the envelope follower running at +/- 12V. I've done an extensive amount of work and testing on this circuit at +/-12V without nary a problem. Ignore those 100pF caps, this schematic is from the 70's when op amps needed compensation. Any modern op amp will work.

For your power supply question, you can surely just leave that -12V rail open. Shunting it to ground will just burn up power without reason.

[mills]

Thanks very much for the reply, I appreciate the help!  I'd hoped that was the case with the compensation caps.