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Old 4th April 2011, 01:15 AM   #1
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Location: Quebec, Canada
Default Virtual ground / Rail Splitter using only LM317

Hey guys,

sorry for this probably very basic question, but with the mess that the "search" function is returning I could not easily find my answer.

I wated to build a rail splitter for a headphones amp out of what I had in stock.
And I have Lm317 and only that.

So I've designed a circuit that works when simulating it.
I wanted your opinion.
Would that work ?

(the strange resistors values comes from what I have in stock too).

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Old 6th April 2011, 03:09 PM   #2
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Location: Jackson,michigan
A cheaper method would be to use two resistors of equal value as described here

op-amp with virtual ground in SPICE

If a lower impedence is required than what the resistor divider provides then it can be followed by a unity gain opamp and the output of the opamp becomes the virtual ground. jer
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Old 6th April 2011, 03:18 PM   #3
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Using lower values of resistor lowers this impedence but it also increases the current draw on the power supply.
The opamp buffer allows a lower impedence for the virtual ground.
This works of course depending on your application and current levels required returning to the virtual ground. jer
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Old 6th April 2011, 03:44 PM   #4
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The posted schematic cannot work.
Because current from U2 is one way only.
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Old 6th April 2011, 03:52 PM   #5
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It just does not strike me as efficient enough for a portable application like a headphone amp on a battery.
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