What's a good medium-power opamp? I need to source/sink at least 60mA, with say +-7.5 volt supplies, and swing +-6 maybe. No particularrequirements otherwise.I suppose I could boost a cheap SOT-23 opamp with a couple of cheapSOT-23 emitter followers.... v+ | c \ +----Rb---b npn \ | e \ | | \---------+----Rx----+------- / | | / | e / +----Rb---b pnp c | v-but a single part would be nice; I have to do this 16 times on asmallish board.John

Your suggested approach is probably the least fraught with possiblestability problems.But when I need lots of near-rail-to-rail swing I put resistors in theVCC and VEE lines and add the transistors there (e.g., base to VCCpin, emitter to rail, collector to output point... if you don't needrail-to-rail, tie OpAmp output to collectors). ...Jim Thompson-- | James E.Thompson, P.E. | mens || Analog Innovations, Inc. | et || Analog/Mixed-Signal ASIC's and Discrete Systems | manus || Phoenix, Arizona Voice:(480)460-2350 | || E-mail Address at Website Fax:(480)460-2142 | Brass Rat || | 1962 | America: Land of the Free, Because of the Brave

power opamp?

Mar 02, 2008 41 Replies

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Rene Tschaggelar 18 years ago

Sorry Jim, you're right. I realized that after having read a few more messages than I did at the beginning.

Rene

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Jim Thompson 18 years ago

[snip]

No problem. I'm glad someone else mentioned it. It's reasonably stable when tied to the OpAmp output.

I used a similar configuration in the early '70's, no NPN, R to ground from OpAmp output, PNP directly to load (not tied to OpAmp output),

741 OpAmp, to make LDO's for the TOW missile, built as a hybrid in a TO-3 package ;-)

...Jim Thompson

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