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Homework Help: Inverting Operational amplifier

  1. Feb 19, 2007 #1
    1. The problem statement, all variables and given/known data
    1) Consider an inverting operational amplifier as shown in figure. Suppose R1= 1000 ohm & Rf = 10^6 ohm. It is said that the input impedance=R1=1000 ohm and the Output impedance= 0.

    2) Consider a non inverting operational amplifier as shown in figure. Suppose R1= 3500 ohm & Rf = 15000 ohm. It is said that the input impedance=infinite. Why is it so? Here Rf is the feedback resistor.But only for an ideal Op-Amp, the input impedance is infinite and not for a real one, isn’t it? So, can R1 be taken as the input impedance of the Op-Amp in both cases?

    2. Relevant equations

    3. The attempt at a solution

    Attached Files:

  2. jcsd
  3. Feb 19, 2007 #2


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    Gold Member

    These are a couple of links that explain the input impedance for both op amps.
    http://www.phys.ualberta.ca/~gingrich/phys395/notes/node102.html [Broken]
    http://www.phys.ualberta.ca/~gingrich/phys395/notes/node103.html [Broken]

    For a real non inverting op amp, the input impedance is somewhere between 1 MΩ to 10 TΩ.
    Last edited by a moderator: May 2, 2017
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