input voltage for op amp

Discussion in 'General Electronics Chat' started by TAKYMOUNIR, Sep 10, 2011.

  1. TAKYMOUNIR

    Thread Starter Active Member

    Jun 23, 2008
    351
    1
    why the input(the 2 input +&-) for op amp are the same(negative feed back)
    how can i prove this
     
  2. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,674
    2,724
    There is nothing to "prove". This is by definition for an op amp operating closed loop. Actually, there will be a small difference (ignoring input offset voltage) due to the finite open loop gain. The difference * (open-loop gain) = output. The open-loop gain is usually so large that it can be ignored in most cases, and the assumption that in+ = in- is valid.
     
    TAKYMOUNIR likes this.
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