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Homework Help: Op Amp Capacitance multiplier

  1. Aug 7, 2010 #1
    1. The problem statement, all variables and given/known data

    Please, I would like to know how to find the factor by which the capacitance is multiplied
    A picture of the Op Amp is here: http://en.wikipedia.org/wiki/File:Cap-mult-op.svg
    Zc is complex impedance of C

    2. Relevant equations

    none given
    3. The attempt at a solution
    choose,
    I2 through R2 left to right
    I1 through R1 top to bottom

    so Iin = I1+I2 = (Vin-Vout)/R2 + Vin/R1 +Zc
    Vout =V- = V+ = (ZcVin)/(R2+Zc)
    ...
    Iin=Vin((R2+R1)/(R1(R2+Zc)))

    And then I'm not sure how to calculate the effective capacitance. I think it is supposed to be increased by a factor of R2/R1 but I dont know how to get that.
     
  2. jcsd
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