testing the integrity of an opamp?

[Guest]

How to test an opamp? Can you do it with a multimeter? I'm troubleshooting the A12 (api-type) thing and I'm wondering how to tell if I've fried it.

Thanks...

kb

 

[gyraf]

Can you do it with a multimeter?

No. You'll have to put it to work, and see how it behaves.

Jakob E.

 

[Guest]

[quote author="gyraf"]

No. You'll have to put it to work, and see how it behaves.

Jakob E.[/quote]

Like give it a shovel? :grin:

Is it tested with a scope at the output?

Thanks.

kb

 

[SSLtech]

testing the integrity of an opamp?

Leave it alone in a room with your wallet for ten minutes and see if all your money is there afterwards! :wink:

Seriously though, no single test will check for subtle differences between chips, but since so many share pinouts, a fave trick is to wire up an IC socket to form a slow oscillator (1Hz or so) and run a pair of LEDs (with series resistors between the rails and the output...they should 'wig-wag' if the op-amp works.

In circuit testing you have to look at the schematic. A totally dead ship will still often show signal present at the output pin if it's used in an inverting mode... the feedback resistor between the incoming signal (at the inverting input) and the output pin will deceive you... the signal will often be slightly lower than the input, but a simple "scope-it-at-it's output" isn't such a simple "go/no-go" test as it first appears.

(of course your biggest clue in the fault as described above is that the signal -though slightly weaker- will also be inverted compared to the polarity if the op-amp was working correctly.)

Keith