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Old 28th March 2004, 05:49 PM   #1
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Angry single supply for lm3886

Can someone explain how a single supply works?
I want to build an amp using lm3886s, but my ps is +/- 50v. I want to use +50v and 0v to power the amp. I've looked at the schematic, but I still don't get how it works. One side of the speaker coil is connected to gnd, but what goes into the other side of the coil? +50v from the amp? That will only move the speaker one way.
Will a single supply move the speaker both ways?
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Old 28th March 2004, 08:32 PM   #2
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As with most single voltage amplifiers, there's a cap between the output and loudpeaker that "eats" the offset voltage.

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Old 28th March 2004, 08:46 PM   #3
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First check the datasheet of the LM3886 carefully.

How it works?

The input signal is lifted up to (in your case) 25 volts. This means you will get 25 V out when you have no signal. When you apply signal the out will swing around 25 volts. This 25 V DC is filter out by a large electrolytic cap, 4700-10000 uF. Your speaker is connected with this huge capacitor is series and then connected down to ground.

Just check page 6 in the datasheet.
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Old 28th March 2004, 08:53 PM   #4
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Would bridging 2 lm3886s both running off a single supply work the same way as if they were running off a +/- supply?
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Old 4th April 2004, 10:18 PM   #5
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anyone?
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Old 5th April 2004, 01:03 AM   #6
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Quote:
Originally posted by xplod1236
Would bridging 2 lm3886s both running off a single supply work the same way as if they were running off a +/- supply?
If you bridge 2 LM3886's built single-supply per the datasheet schematic, you need a phase splitter in front of them since both chips will be non-inverting. Something like a DRV134 will do the job of buffering and phase splitting before the LM3886 stage.
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