555 EFI

[Frederic Breitwieser]

> OK, I found a diagram for a summing amp, but is uses a dual polarity
> power source, anyone got a clue for how to do a summing amp with
> just +5v power supply?.  Or can it be done with a single?.

Easy... I've done this before... however certain op-amps,
with JFET inputs tend to lose some consistancy in their
amplifications or inverting... the LM324 and the 741 and
741C do just fine.

Put a 1k resistor between +V and the "virtual ground" and a
1k resistor between -V (real ground) and the "virtual
ground".  Then, you have a split power supply for Op-Amps. 
This works very well, and I've done this many, many times
for little amplifier projects where the pre-amp stage needed
to have a split powersupply, and I  didn't want to run two
9V batteries, just one.  Can you picture it, or should I do
a quickie GIF tomorrow?




-- 
Frederic Breitwieser
Bridgeport, CT 06606

http://www.xephic.dynip.com
1993 Superchaged Lincoln Continental
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