Microphone Help: Constant Amplitude w/ No Input

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SUMMARY

The discussion centers on an OPamp circuit designed to amplify microphone input, specifically addressing the issue of constant amplitude output even when no sound is present. The OPamp gain is set to 500, which is likely contributing to the observed behavior. Participants suggest that the constant amplitude may be due to noise interference, particularly from nearby fluorescent lights or rectified AC mains noise at frequencies of 100Hz or 120Hz. This indicates that the circuit may require additional filtering to mitigate unwanted noise.

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rama1001
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Hello,
I have a circuit that can take the input from microphone and amplify it with OPamp. I have connected everything correct and when i check the output whit no input at microphone still i get output with constant amplitude. I think that was due to gain of OPamp but not sure. The opamp gain is 500 and when if there is any input(song or sound) at microphone it just following the song. Please clear me why i am getting these constant amplutude when there is no input. Is this really due to gain. Please see the image when there is no input.
 

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rama1001 said:
Hello,
I have a circuit that can take the input from microphone and amplify it with OPamp. I have connected everything correct and when i check the output whit no input at microphone still i get output with constant amplitude. I think that was due to gain of OPamp but not sure. The opamp gain is 500 and when if there is any input(song or sound) at microphone it just following the song. Please clear me why i am getting these constant amplutude when there is no input. Is this really due to gain. Please see the image when there is no input.

Looks like 100Hz (or 120Hz) noise from rectified AC Mains noise. Are there flourescent lights nearby?
 

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