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-   -   Splitting a supply (http://www.diyaudio.com/forums/solid-state/42782-splitting-supply.html)

jackinnj 18th October 2004 12:02 PM

Splitting a supply
 
A circuit similar to this appeared in the most recent issue of AudioXpress ("MaxxBass Subwoofer") for splitting a wallwart supply into regulated +/- 5VDC -- this one won't oscillate!

http://www.tech-diy.com/splitsupply.gif

Steven 18th October 2004 06:15 PM

Re: Splitting a supply
 
Quote:

Originally posted by jackinnj
...this one won't oscillate!

But it won't work either. Your biasing is wrong, trying to force the opamp output to a negative voltage compared to the non-inverting input, which is at the negative supply rail of the opamp.

Steven

jackinnj 18th October 2004 06:58 PM

Re: Re: Splitting a supply
 
Quote:

Originally posted by Steven


But it won't work either. Your biasing is wrong, trying to force the opamp output to a negative voltage compared to the non-inverting input, which is at the negative supply rail of the opamp.

Steven

I flipped the OPAMP (vertically) by mistake -- mea culpa -- incidentally, the schematic is also on National Semi's website --

jackinnj 18th October 2004 07:27 PM

here's another go:
http://www.tech-diy.com/splitsupply2.jpg

djk 19th October 2004 08:36 AM

Radio Shack sells several wall warts that are AC, I bought one the other day to replace one in a JBL BX63 electronic crossover.

Half wave rectify it for both supplies, then regulate it.

darkfenriz 19th October 2004 08:37 AM

doesn't it multiply the input offset voltage of the opamp by 15x
????
with the regulated voltage that small may be noticable...
am I right??

jackinnj 19th October 2004 12:51 PM

Quote:

Originally posted by djk
Radio Shack sells several wall warts that are AC, I bought one the other day to replace one in a JBL BX63 electronic crossover.

Half wave rectify it for both supplies, then regulate it.

I have used an AC wall wart from a Sony answering machine -- you use a voltage doubler -- the ground is the junction of the two capacitors which are attached to the AC source.

AndrewT 18th October 2006 08:36 AM

Hi,
what's the lowest supply voltage this circuit can accept?
output=10Vdc
Min input =? when loaded.


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