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Operational Amplifier Homework Question

  1. Dec 8, 2016 #1
    1. The problem statement, all variables and given/known data
    What is the value of V2 in terms of Vos?

    2. Relevant equations


    3. The attempt at a solution
    In the class, we were told that this is just a non-inverting amplifier, thus V2= Vos x (R2/R1+R2).
    However, I want to work out the solution by applying nullator hypothesis (voltage difference between the two op amp inputs is 0) only, without realising that the top part is a potential divider.

    Is it correct to assume that the voltage across R1 is Vos? That way, I can get the current i to solve for the voltage across R2.
    http://[PLAIN]http://i64.tinypic.com/a0i5hs.jpg [Broken]
    http://i64.tinypic.com/a0i5hs.jpg

    upload_2016-12-8_12-34-15.png
     
    Last edited by a moderator: May 8, 2017
  2. jcsd
  3. Dec 8, 2016 #2

    gneill

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    Staff: Mentor

    Yes, that's a valid assumption here.
     
  4. Dec 11, 2016 #3

    rude man

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    Homework Helper
    Gold Member

    A non-inverting op amp gain is always >=1 unless the feedback is active (another amplifier section). So I hope you were not told that ...
    ... and I assume you meant Vos x R2/(R1+R2) otherwise your equation is dimensionally wrong.
     
  5. Dec 12, 2016 #4

    LvW

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    Yes - with this assumption you get I=Vos/R1=(V2-Vos)/R2.
    This equation can simply be solved for V2.
     
    Last edited by a moderator: May 8, 2017
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