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Op Amp Design #2

  1. Mar 6, 2014 #1

    Maylis

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    1. The problem statement, all variables and given/known data
    Design a circuit containing a single op amp that can perform the following operation: Vo = 3*10^4(i2-i1), where i2 and i1 are input current sources


    2. Relevant equations



    3. The attempt at a solution
    Where I'm at right now, I am just using the equation for a difference amplifier gains, but I have more unknowns than equations, so I don't know what to do.
     

    Attached Files:

  2. jcsd
  3. Mar 7, 2014 #2

    NascentOxygen

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    Hi Maylis. Could I suggest that you post images as unadorned jpeg (or png, etc) files, so those using basic tablets (and costly data plans) are still able to participate?
     
  4. Mar 7, 2014 #3

    Maylis

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    Alright, here is a .png
     

    Attached Files:

  5. Mar 7, 2014 #4

    rude man

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    Your diagram labeling does not agree with your equations.

    Big hint: since the inputs are current you need a total of only 2 resistors.
     
  6. Mar 7, 2014 #5

    Maylis

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    Oh I see, I need to change the label of R2 and R3. Either way my problem persists. The equation should be correct now with that change, as well as making it R3*i2 in my second stop
     
    Last edited: Mar 7, 2014
  7. Mar 7, 2014 #6

    Maylis

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    Okay, I source transformed, corrected the labeling, and this is what I came up with.

    Edit: my bad, I was saying that no current goes through R1 and R3, which cant be possible since there is a potential difference between Vn/Vp and the resistors. Now the equations are even messier. Where do you get the fact that I only need 2 resistors from? I am following the template for a difference amplifier as given in the textbook and I redrew as my original image, pre-source transform
     

    Attached Files:

    Last edited: Mar 7, 2014
  8. Mar 7, 2014 #7

    NascentOxygen

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    See if you can get it to work without R1 and R3.
     
  9. Mar 7, 2014 #8

    rude man

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    And RL.


    And BTW the pdf file is a lot easier to read, for me anyway.

    If the new tablets, iPads etc etc can't even read pdf files any more I am more po'd than ever that xp is disappearing ... we are dumbing-down at an ever-increasing rate ... :grumpy:
     
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