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Homework Help: Inverting Op-Amp Problem

  1. Dec 7, 2007 #1
    1. The problem statement, all variables and given/known data

    For the attached circuit: R1=1Mohm, R2=10Mohm, C1=1uF. If the initial capacitor voltage is 0, find the output. Will this circuit work in practice? Explain. What does this circuit do??

    What does this circuit do? This circuit integrates and is a low pass filter.
    Will this circuit work in practice? I don't see why not.

    The ouput voltage is equal to the voltage across the capacitor which in this case would be 0. I believe R2 is used to avoid saturation.

    Am I correct in all this?

    Attached Files:

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  3. Dec 7, 2007 #2
    Your image is still pending approval. If you need help immediately then upload on imageshack or something.
  4. Dec 8, 2007 #3
    I think the image is ready now. Would the output voltage possibly be whatever the voltage is across the capacitor? In this case, 0??
  5. Dec 8, 2007 #4
    The circuit is an integrator. Yea I believe the voltage out will be the voltage across the cap. Because the cap will charge to its max and become effectively an open circuit.

    There is a formula for analyzing for an AC source for Vout.
  6. Dec 8, 2007 #5


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    Wouldn't the output be measured from the op-amp output to ground?

    "Will this circuit work in practice?" What would happen if the input signal went below ground (negative)? Hint: How would this be effected by the op-amps' power supply?
    Last edited: Dec 8, 2007
  7. Dec 8, 2007 #6
    You got me dlgoff. I don't know.
  8. Dec 8, 2007 #7


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    If the op-amp is a single supply type; say +15volts and ground, and the signal went below ground (negative) the output would get "clipped". Now if you use a duel supply type; say ±15volts, you can drive the input below ground and get a "clean" output.
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