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Operational Amplifier Circuit

  1. Mar 29, 2014 #1

    dwn

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    1. The problem statement, all variables and given/known data
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    2. Relevant equations

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    3. The attempt at a solution

    The answer is given, but I do not understand how they got it. When I multiply 9mA and 947.308Ω resistor, I get 8.526...what am I doing wrong? Also, could someone explain how they went on to get the final voltage in the simplified circuit. Don't you just add voltages when they are in series like this...?
     

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  3. Mar 29, 2014 #2

    gneill

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    Staff: Mentor

    8.526 V + 5.4 V = 13.926 V. So what's the problem?
     
  4. Mar 29, 2014 #3

    dwn

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    According to their calculation they got .947 V
     
  5. Mar 29, 2014 #4

    dwn

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    What does the Rf represent as well?
     

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  6. Mar 29, 2014 #5

    AlephZero

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    9 x 0.947 = 0.947 is obviously wrong, and looks like a typo.
    It should be 9 x 0.947 = 8.523.
     
  7. Mar 29, 2014 #6

    dwn

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    I haven't built up a lot of confidence with circuit analysis, so I wanted to make sure that it was in fact an error on there part. Thanks guys.
     
  8. Mar 29, 2014 #7

    gneill

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    Staff: Mentor

    For what? We need some context here.

    Rf is the resistance in the op-amp feedback path.
     
  9. Mar 29, 2014 #8

    AlephZero

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    The feedback resistor. 150k + 0.740k in series.
     
  10. Mar 29, 2014 #9

    dwn

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