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Am I on the right track in solving this OpAmp problem?

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  1. Mar 31, 2016 #1
    1. The problem statement, all variables and given/known data

    px1.JPG
    2. Relevant equations
    H(s)= Vo / Vi
    Ideal op amp:
    V+ = V-
    Vo = V-

    3. The attempt at a solution
    To simplify the circuit, I noticed that the 200 ohm resistor and 60 microFarad capacitor are in parallel so:
    Zp = (R/sC) / [(1+sRC)/(sC)] = R / [(1+sRC)]

    Seeing that the Zp is in series with the 5 ohm resistor, I went ahead and used the voltage divider in search of Vo / Vin for the transfer function:

    V- = 5 / [ 5 + (200/1+s(200)(60^-6)) ] * Vo

    This is the part where I stopped since I'm not quite certain on how I can relate this to Vin. Can somebody lead me to the right track?
    Thank you!
     
  2. jcsd
  3. Mar 31, 2016 #2

    NascentOxygen

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    Staff: Mentor

    For an OP-AMP with very high gain (ideally infinite), it causes V+ = V-

    For your configuration here, V+ = Vin
     
  4. Mar 31, 2016 #3
    Okay cool, I get an answer of:

    H(s) = 5 / [ 5 + (200/1+s(200)(60^-6)) ]

    Does this look correct?
     
  5. Mar 31, 2016 #4

    NascentOxygen

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    Staff: Mentor

    A little clumsy; it is usually written in a more standard form. I think you'd be needing more parentheses there, to make it universally correct.
     
  6. Mar 31, 2016 #5
    H(s) = 5 / [ 5 + 200 / (1+s(200)(60^-6)) ]

    And yes I know I have to make it in standard form, but am just verifying
     
    Last edited: Mar 31, 2016
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