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Old 18th October 2004, 12:02 PM   #1
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Default 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!

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Old 18th October 2004, 06:15 PM   #2
Steven is offline Steven  Netherlands
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Default 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
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Old 18th October 2004, 06:58 PM   #3
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Default Re: Re: Splitting a supply

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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 --
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Old 18th October 2004, 07:27 PM   #4
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here's another go:
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Old 19th October 2004, 08:36 AM   #5
djk is offline djk
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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.
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Old 19th October 2004, 08:37 AM   #6
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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??
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Old 19th October 2004, 12:51 PM   #7
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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.
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Old 18th October 2006, 08:36 AM   #8
AndrewT is offline AndrewT  Scotland
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Hi,
what's the lowest supply voltage this circuit can accept?
output=10Vdc
Min input =? when loaded.
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