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Homework Help: OP amp circuit problem

  1. Jan 21, 2008 #1
    1. The problem statement, all variables and given/known data
    The op amp circuit shown bellow is intended to provide any gain between -10 (for k=0) and +10 (for k=1) by adjusting the potentiometer. Let R1 and R2 have the scaled values, show that..

    V2/V1= {r1/(r1+10k)} [-11/{1+(10kr1/r1+10k)}] + [r2/r2+10(1-k)] [1+ {11/1+10kr1/r1+10k}]


    2. Relevant equations



    3. The attempt at a solution

    i have no idea how to write nodal equations for a potentiometer. If any one tell me how to do that, i can figure out the rest by myself. thanks
     

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  2. jcsd
  3. Feb 21, 2008 #2
    Think of the potentiometer as 2 resistors in series with values 10k and 10(1-k). That's all.
     
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