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high voltage "opamp"

+12V
+36V

signal.

or

Possibly you're thinking about National Semiconductor AN-272, "Op Amp Booster Designs". Look particularly at Figure 6.

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But there are many high voltage op amps that will do the job for you as a one chip solution. One you might want to try is the TI (formerly Burr-Brown) OPA452, which is available and in stock from Digi-Key for $5.10 USD in single quantities. It comes in a 7-pin TO-220 package. The +/-40V max supply voltage (+/-36V output) OPA452 has a GBW of

1.8MHz, it's unity gain stable, and can source or sink 50 mA continuously. It also has current limit and thermal shutdown.

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There are several subtle and not-so-subtle difficulties with output voltage boosters for op amps that degrade performance. And you have to pay some extra attention to op amp input protection, particularly transients. You'll almost always end up looking better and getting better performance with a single chip solution if it's available.

Good luck Chris

Reply to
Chris
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Is there a standard circuit connection that can be used to raise the output swing of an opamp to a higher voltage ? For example, a TL084 opamp with a +18V / -18V supply can give an output swing of about +12V to -12V. But what I am looking for would permit a voltage swing of +36V to -36V. I would of course expect to provide higher voltage power rails, and add a few discrete transistors, etc., to massage the signal.

It seems like this circuit has been used as an example in an app note or text book somewhere, but I haven't located it.

Ideas, anyone?

Reply to
mw

One method is to drive the op-amp's power pins ( only works for a single device ) with emitter ( or source ) followers driven by voltage dividers between the op-amp output and the high voltage supply rails.

You can source more current if required by adding emitter followers to the output pin directly.

Graham.

Reply to
Pooh Bear

Yes. That's the one.

I just now simulated various versions of the National circuit and did find that they do not perform well at high frequencies (>20kHz). I think it is because impedances are too high. It's the trade off between speed and power.

Thanks for yours (and Pooh Bear's) help.

Reply to
mw

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