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Op-Amp Current Gain with current source

  1. Mar 5, 2014 #1


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    1. The problem statement, all variables and given/known data
    Problem #6 on the attachment

    2. Relevant equations

    3. The attempt at a solution
    I am stuck because if I do KCL at the node above the current source, It seems like all of the current should go back into Rs and none from the current source goes up to Rf

    Attached Files:

    • 5.6.jpg
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    Last edited: Mar 5, 2014
  2. jcsd
  3. Mar 5, 2014 #2


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    You forgot the attachment but I found it on another thread.

    The current through Rf is typically written as (Vo-Vi)/Rf.
  4. Mar 5, 2014 #3

    rude man

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    There are two sources of current into Rs, not just one!

    EDIT: donpacino is right. No current into Rs.
    Last edited: Mar 5, 2014
  5. Mar 5, 2014 #4


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    you want iL/is

    with negative feedback, the positive and negative nodes of the op-amp should equal each other. so the negative node=0V

    since the voltage at the negative node is zero, with an ideal steady state op-amp no current can flow through Rs.

    so the current through rf is Is.

    Use that to get you started
  6. Mar 5, 2014 #5


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    I have it solved, thank you!

    I got G = -Rf/RL
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