Op-amp oscillation testing
post-808645
Thread Starter
Post #1 of 5

Tobrew

New Head-Fier
Joined
Mar 21, 2004
Messages
18
Reaction score
0
Joined
Mar 21, 2004
Posts
18
Likes
0
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?
 
     Share This Post       
post-808673
Post #2 of 5

tangent

Top Mall-Fi poster. The T in META42.
Formerly with Tangentsoft Parts Store
Joined
Sep 27, 2001
Messages
5,969
Reaction score
55
Joined
Sep 27, 2001
Posts
5,969
Likes
55
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.
 
     Share This Post       
post-808898
Post #4 of 5

Tobrew

New Head-Fier
Joined
Mar 21, 2004
Messages
18
Reaction score
0
Joined
Mar 21, 2004
Posts
18
Likes
0
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?
 
     Share This Post       
post-808975
Post #5 of 5

beerguy0

Headphoneus Supremus
Joined
Apr 5, 2004
Messages
2,413
Reaction score
22
Joined
Apr 5, 2004
Posts
2,413
Likes
22
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
 
     Share This Post       

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top