Op-amp oscillation testing
May 18, 2004 at 8:52 PM Thread Starter Post #1 of 5

Tobrew

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How do you test an op-amp for oscillation and what are the symptoms of an op-amp that is oscillating? Also, if it is a two channel op-amp can you get oscillation on just one channel?
 
May 18, 2004 at 9:17 PM Post #2 of 5

tangent

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Quote:

How do you test an op-amp for oscillation


1. Put an oscilloscope on it and look.

2. Measure the current draw of the circuit. Is it higher than you expect? Is it equal to the maximum current draw of the circuit?

3. Put an AM radio near it and tune it to see if you can pick up an RF noise spike. (Good for very high frequency noise, when your scope won't go fast enough.)

4. Look for unusually large DC offsets.

There are probably other ways...

Quote:

if it is a two channel op-amp can you get oscillation on just one channel?


Any single gain block with a feedback path can oscillate.
 
May 19, 2004 at 12:35 AM Post #4 of 5

Tobrew

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Quote:

Originally Posted by tangent
1. Put an oscilloscope on it and look.


I assume I would measure the Op-amp signal ouput compared to ground. Is that correct?
 
May 19, 2004 at 1:20 AM Post #5 of 5

beerguy0

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An ideal way to see if you have an oscillation problem is to look at the output with a spectrum analyzer, but most DIY'ers don't have these lying around.

An oscilloscope can help, but again, not everyone has one.

Heat is a good indicator. Parts that oscillate tend to run very hot. Give it the pinky test:wink:

Excessive current draw (which produces heat).

Cheers,

bg
 

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