How easy is it to drive an op-amp from a 9v battery?

[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?

[cuibono]

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?

[MikeHunt79]

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.

[BWRX]

Try searching for "rail splitter".

[MikeHunt79]

Ok, thanks... Hopefully it shouldn't be to complex.

[Dxvideo]

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.

[peranders]

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

[EWorkshop1708]

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.

[renfrow]

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.