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Homework Help: Differentiating Op Amp circuit help

  1. May 21, 2012 #1

    FBS

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    1. The problem statement, all variables and given/known data
    (See attached figure) I need to find V0 in terms of R1, R2, R3 and C.


    2. Relevant equations
    V0 = -RC (dVs/dt) for a differentiator


    3. The attempt at a solution
    I understand I have to apply KCL at the node between C and R1, and I've also determined that R1 and R2 are in series (not sure) but I don't know what to do with R3.

    {C * (d(Vn - Vs)/dt)} + {(Vn - V0)/(R1 + R2)}
     

    Attached Files:

  2. jcsd
  3. May 21, 2012 #2
    Hey Did u notice that the node between C and R1 is a virtual ground.
     
  4. May 21, 2012 #3

    rude man

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    Homework Helper
    Gold Member

    Plus you're missing one node, plus your equation is incorrect I'm afraid.

    Just write the KVL for every node correctly & it'll be obvious what to do with R3 ....
     
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