I am working on an op amp project and was wondering if someone could explain common mode voltage, in the context of op amps and in general. From what I have read it is voltage that is common to both inputs of the op amp and is not desirable.

Thanks

 

Originally posted by Coz@May 13 2005, 07:38 PM
explain common mode voltage, in the context of op amps and in general. From what I have read it is voltage that is common to both inputs of the op amp

Yes, exactly.
If you have a signal which appears simultaneously at both inputs it is called a common-mode signal and will not be amplified.
One of an op-amp's properties is called its common-mode rejection ratio.
You can read about it in more or less any op-amp tutorial.