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Op amp transfer function determination (need help)

  1. Dec 8, 2015 #1
    • OP warned about not using the homework template
    Hey guys, need help with a problem here.

    Sorry for the quality of the image.


    I understand that above the op-amp, is the active low pass filter. So if I were to figure that out with respect to V2 and Vout, it would just be

    Vout/Vs = -(Zf/Zs)


    Zf = (Rf/(1+jwCfRf))
    Zs = Rs

    But I don't understand how the bottom setup comes into the equation. I realize it must also be a filter and should be solved wrt V1.

    And I am asked to find the transfer function Vout/V1-V2.

    All help would be greatly appreciated.
  2. jcsd
  3. Dec 9, 2015 #2


    User Avatar

    Because you have two input sources you can derive two different transfer functions (one inverting and the other one non-inverting).
    And - as a second step - it should not be a problem to substract both functions Vout=Vout1-Vout2.
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