Power supply design for power operational amplifier

First: take care. 100V is getting into the range where it can be fatal on a bad day, and if you get one hand on the +100V and another on the

-100V, it can be fatal even on a not-so-bad day. So take all due precautions when you're working on your circuit.

If you don't know what all the due precautions are, get your hands on an ARRL Handbook, or ask here. The basic idea is that you never, ever want lots of current flowing through your heart.

Second: You may not need regulated power. Depending on the power supply rejection ability of the amp, you may be able to just use an isolation transformer, bridge rectifier, and filter caps. Figuring this out is something you'll have to do on your own.

Third: If you must have regulated power, that's a project in itself. I'd start with op-amps, with ye olde zeners and pass transistors, or with the LM723 which was still around as of five years ago, and will probably still be around when I dry up and blow away from old age.

I used a PA91 (or so) in an amplifier with a +/-200V output. If I recall correctly, the power supply was just a transformer, bridge (or

• and - full wave) rectifier, and suitable filter capacitors - no regulation. The physicists using the things haven't complained about the performance.

How about a transformer with 3 or 4 windings, and a Tube type 80, a couple of 16 mfd electros and an old speaker field coil for a choke.

This sort of stuff was so commonplace once. Are you integrated chip specialists wimps when it come to voltages over 5?

John G.

That would work.

I'm not sure what you're trying to be snide about. The OP declares that he doesn't know much about electronics, and it very much sounds like he's doing a one-off.

You want he should spend a year learning how to design a switching supply that'll do this all in four cubic inches of space, while watching his market window snap shut?

Perfection is the enemy of good enough.

I didn't read John. G 's response as being snide...just a little friendly good humour that's all. Of course nobody expects this guy to become an electronics designer overnight...however tubes and chokes are old technology and not so easy to learn about in this day and age...to wit..."the art of electronics" by H & H-nothing about thermionic valves...sure old ARRL books will have stuff as my old Mullard tube manuals do..but not so easy to get hold of nowadays especially if one is not from an electronics background. just my tuppence worth (shows my age) Daniel

become an electronics designer overnight...however tubes and chokes are old technology and not so easy to learn about in this day and age...to wit..."the art of electronics" by H & H-nothing about thermionic valves...sure old ARRL books will have stuff as my old Mullard tube manuals do..but not so easy to get hold of nowadays especially if one is not from an electronics background. just my tuppence worth (shows my age) Daniel

Thanks Daniel, It was meant to be lighthearted. Who would use an 80 when you could get a

John G.

snipped-for-privacy@u39g2000pru.googlegroups.com...

Sorry if I misread your intent.

All I was trying to do (and Peter, too, I think), was point out that you often don't need some whiz-bang* switching, or even regulating, supply to make an op-amp power supply. Just a transformer, filter, and rectifier of any stripe whether it's silicon, vacuum or electrolytic.

• with potential emphasis on the BANG if you get the control circuits wrong.

When I was in 12th grade physics, there was a little room behind the classroom where they had a scope, and an old TV and a whole bunch of other physics-class-ey stuff; I thought I'd measure the waveform at the plate cap of the horizontal output tube. Had the scope on 100V/div or whatever - I knew it was going to be more than just a couple of volts!

Drew an arc to the probe at least 2" long. Nothing got hurt - it was a tube-type scope (tek 545-style).

Ah, those were the days! ;-)

Cheers! Rich

Someone who had the 80s and plenty of 4 pin sockets. Some manufacturers even switched back to the 80 because it was the same tube, but cheaper, or surplus.