Power opamp.. output "near" the rails.

You might parallel a bunch of these

It's a cheap little rail-to-rail amplifier, but the output stage can deliver quite a lot of current - 80mA. Put a quad package's worth - MC33204 - in parallel and you might get your 300mA.

The quad costs a a couple of dollars in small quantities, and Farnell/Newark seem to have plenty. Joerg wouldn't like it, but your customers have deeper pockets.

What about this bad boy right here?

Or bootstrap the supply rails? Or both?

Hmm OK thanks Bill, the power opamps I'm looking at are ~$5 so price is OK. It will have to dissipate ~1 Watt (worse case) (I forgot to share that spec.) I was looking for something with a thermal power pad or similar.

George H.

I've got that bad boy in my parts box... never used. It might have to dissipate 1W.. which makes me a little nervous.

I'm not sure what you mean by boot strapping the supply rails?

George H.

TCA0372, dual 1 amp, 45 cents.

Golly Mr. Wizard, good suggestion!

By Apex, are you referring to a specific trade mark or something else?

What is your frequency response requirement ?

Some amplifier for low voltages use voltage amplifier output stages (not emitter followers) so you get close to rail to rail.

An car audio amp would work with at least +/- 7 V and would deliver sufficient currents for your requirements.

We've used them in several products, and they seem well behaved. Not c-load stable, but you can work around that.

Oh sorry, Apex makes HV and power opamps. They were part of my digikey search. I had some bad luck with one of their HV opamps and I've scratched them off my list... well unless I need them again in the future :^) They are spendy too.

Yeah frequency is modest, DC to 10k Hz. Actually this thread should be stopped. I made a mistake in my power calculation and the I can run this off 15 volts rails with lots of head room, ~2W of dissipation. and a power opamp in stock (opa544). (I multiplied 0.2 by 10 and got 5... go figure.)

George H.

This is driving a coil. What sort of power dissipation?

George H.

Driving coils dynamically can get nasty, because it can put an opamp into a high-dissipation quadrant. Better Spice it.

Here's a TCA0372 acting as a programmable power supply with loat of capacitance in the loads. The real thing will use DACs instead of pots.

Hmm... this is fairly low frequency (DC - 10 kHz.) I'm not even sure of the coil parameter, R = 10 ohms, air coil. Can I guesstimate a problem frequency as when I get above the L/R time?

It's someone else's design, I was laying out the circuit and thinking about worse case power dissipation. (which I screwed up.)

George H.

So use a handful of single or dual parts. One watt spread across several packages isn't going to be a problem.

One watt at 300mA is a 3.3V drop. A resistive load to ground from +/-5V supplies would give a peak dissipation in the op amp at +/-2.5V times 150mA which is 0.375W.

You spec did need more detail.