How easy is it to drive an op-amp from a 9v battery? - diyAudio
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Old 28th March 2008, 02:43 AM   #1
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Default How easy is it to drive an op-amp from a 9v battery?

I've seen some portable headphone amps that do it, they mention something about "floating ground". Do they simply use a voltage divider, or is it a little more complex than that?
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Old 28th March 2008, 02:48 AM   #2
cuibono is offline cuibono  United States
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I use two 9v batteries, in series. Gnd comes off the middle of the two, giving +/-9V. I'd guess this is what they mean...

Typically 9V batteries are rated at a current of 15mA. I wonder if that is enough?
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Old 28th March 2008, 03:00 AM   #3
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15mA should be fine (I think)....

I really want to power it from a single battery if I can, but if not I guess I can use 2... I'll need a bigger enclosure then tho.
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Old 28th March 2008, 03:15 AM   #4
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Try searching for "rail splitter".
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Old 28th March 2008, 09:03 AM   #5
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Ok, thanks... Hopefully it shouldn't be to complex.
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Old 28th March 2008, 10:06 AM   #6
Dxvideo is offline Dxvideo  Turkey
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If you use two batteries in series, each rail will sink different amount of current then one of the batteries will die before!
So the rail splitter is better.
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Old 28th March 2008, 11:14 AM   #7
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Default Re: How easy is it to drive an op-amp from a 9v battery?

Quote:
Originally posted by MikeHunt79
I've seen some portable headphone amps that do it, they mention something about "floating ground". Do they simply use a voltage divider, or is it a little more complex than that?
Of cource you can use a passive voltage divider but it consumes power which could sometime be critical. It's better to use an active voltage divider, an opamp or a special IC.

http://focus.ti.com/lit/ds/symlink/tle2426.pdf
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Old 29th March 2008, 01:17 AM   #8
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I prefer the two 9V myself as split supplies.

Yes you can run one battery and use a resistor voltage divider with a filter cap, and it works just fine, but if you can use two batteries, that's less parts you have to use and you get a better voltage swing with 2.

I use the +/-9V battery supply when testing freshly built amp circuit, so I can get the amp working on lower voltage, before I give it the "real" power from the mains transformer. If you accidently short the 9V batteries, no smoke most of the time.
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Old 30th March 2008, 03:40 AM   #9
renfrow is offline renfrow  United States
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Try HeadWize they have a lot of plans for headphone amps, and pointers to kits/pcbs/etc. I've built an amp from this site, use it every day at work and am well pleased with it.

Tom.
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