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fried LM324 quad op amp?

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allaccess

New Member
Please ignore/delete this thread. Problem fixed. Sorry for the inconvenience.

Is it possible for an LM324 to be damaged in such a way as all 4 op-amps still amplify but such a basic circuit fails?

Hello, I am trying to use an LM324 quad op-amp to build a basic function generator but i suspect the chip may be damaged.
When i perform a simple can-it-amplify test, all four op-amps pass: I attach a crystal earpiece to the +input, and an 8ohm speaker and a green LED to the output, and simply tap on crystal earpiece, and i get an audible click from the speaker and a flash from the LED when I perform this test on all 4 op-amps.

However, i have tried multiple google-search function generator circuits and none of them work. I get no square wave, and no reading on my digital scope, including this circuit:


Is it possible for an LM324 to be damaged in such a way as all 4 op-amps still amplify but such a basic circuit fails? I have tried constructing just the 1st stage and still get no square wave or output of any kind on pin 1.
Thanks, allaccess
 
Last edited:

alec_t

Well-Known Member
Most Helpful Member
The LM324 cannot drive an 8Ω speaker.
The first stage shown has a lot of positive feedback which will cause the output to latch at/near one of the supply rails until the input receives a very large signal (which a crystal earpiece is unlikely to provide).
 

schmitt trigger

Well-Known Member
Glad that you were able to solve the problem.

It would still be nice to know how you solved the problem, such that other members can learn from your experience.
 
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