inverting opeational amplifier

Discussion in 'General Electronics Chat' started by sharanbr123, Oct 5, 2014.

  1. sharanbr123

    Thread Starter Member

    Sep 29, 2014
    Hello All,

    I am going through the description of inverting operational amplifier.

    The equation for output voltage is given as,

    Vout/Vin = -Rf/Rg

    In a way, this simply looks like a voltage divider circuit and one can get a larger voltage by keeping Rf/Rg very high. I am not able to appreciate concept of amplifier in this case.

    My initial assumption was that the output would be Vout = Gain * Ve. But I dont see this description in tutorial I am reading.

    Can people coment please.

    PS: I am new to the world of analog
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
    No, supply voltage has nothing to do with the gain except determine where your amp will saturate. The equation is correct.

    Also, remember that ground is the ground of a split voltage supply, normally -15 volts and +15 volts. Ground (common) is the mid-point, 0V. The signal can swing positive and negative of common. Until the amplified signal hits -15 or +15 volts (or something slightly less if the amp cannot swing all the way to the supply rail).