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Old 22nd October 2011, 05:12 PM   #1
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Default Best way to create a dual supply

I've been doing alot of research into creating a bi-polar supply from a single one and ran into quite alot of options. I have one extra requirement, the load will not be balanced across the supply. The dual supply will be powering a headphone amp but the positive rail will also be used to power a microcontroller.

My first design failed because I didnt consider this, the rails became very unbalanced with the extra load.

So I need a design that will source enough current and is immune to loading effects (op amp buffer?). At this point I'd like to use a single AC-AC wallwart rather than a chassis mount transformer. The only way I would consider a transformer is if its a small board mount. It's a headphone amp, I cant have it take up a crazy amount of space.

Thanks for any ideas
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Old 22nd October 2011, 05:28 PM   #2
Elvee is offline Elvee  Belgium
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If there is a constant asymetry, you can use a standard voltage regulator to create the virtual 0.
See an example adapted to your situation:
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Old 22nd October 2011, 05:50 PM   #3
AndrewT is offline AndrewT  Scotland
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All the best ideas are simple.

Thanks for that Elvee.
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Old 22nd October 2011, 06:10 PM   #4
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Or use a rail splitter http://docs-europe.electrocomponents...6b800b853b.pdf

and a separate 7905 for the micro-controller.

vac
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Old 22nd October 2011, 06:24 PM   #5
knutn is offline knutn  Norway
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You could use a voltage doubler. Then you can use a single AC-AC wallwart. And an asymmetric load is not a problem.
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Old 23rd October 2011, 05:51 AM   #6
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knutn,

This will work, but delete C1.
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Old 23rd October 2011, 02:44 PM   #7
knutn is offline knutn  Norway
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Sorry, it was an error in the schematic. Attached is the correct one with 12V AC input as an example.
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Old 23rd October 2011, 05:19 PM   #8
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C1 still better be removed. What would be it's function?
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Old 23rd October 2011, 06:58 PM   #9
knutn is offline knutn  Norway
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C1 is optional - for noise filtering.
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Old 24th October 2011, 03:44 PM   #10
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If you are looking to get a solid half-voltage split, use an LM386 with the inputs left open. The output is automatically biased halfway between the positive and negative supplies and, being a power amp, the current capability is pretty good.
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