555 EFI

[Bruce Plecan]

-----Original Message-----
From: Frederic Breitwieser <frederic.breitwieser at xephic.dynip.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Saturday, January 16, 1999 10:47 PM
Subject: Re: 555 EFI


>> 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?

I think I got it.  Will be trying stuff Mon/Tues so I'll holler if
it gets too smokey here.
Bruce              As nutty as the ecm stuff has gotten,  Doc and
                        Grumpy have renamed the Firebird  Pro Zac
>
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>-- 
>Frederic Breitwieser
>Bridgeport, CT 06606
>
>http://www.xephic.dynip.com
>1993 Superchaged Lincoln Continental
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>