Common mode voltage

Discussion in 'General Electronics Chat' started by Coz, May 13, 2005.

  1. Coz

    Thread Starter New Member

    Nov 5, 2004
    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.

  2. David Bridgen

    Senior Member

    Feb 10, 2005
    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.