Ideal Op-Amp Question

Discussion in 'Homework Help' started by KillerZ123, Jan 30, 2011.

  1. KillerZ123

    Thread Starter New Member

    Nov 25, 2010
    7
    0
    I have an Op-amp that looks like this:

    [​IMG]

    and I am trying to derive this equation for Ix:

    I_{x} = (V_{s})\frac{R_{1}R_{3}}{R_{x}(R_{1}R_{3} - R_{2}R_{4}) + R_{1}R_{3}R_{4}}

    Here is what I have so far:

    V_{-} = (V_{o})\frac{R_{1}}{R{1} + R_{2}}
    V_{-} = V_{+}

    I1 going through R4 is:

    I_{1} = \frac{V_{s} - (V_{o})\frac{R_{1}}{R{1} + R_{2}}}{R_{4}}

    I2 going through R3 is:

    I_{2} = \frac{(V_{o})\frac{R_{1}}{R{1} + R_{2}} - V_{0}}{R_{3}}

    Then Ix is:

    I_{x} = I_{1} - I_{2}

    I am not sure if this is correct up to here?
     
  2. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    You are OK so far. There is a very good simplification to be done in the I2 current formula.

    Add the equation V+=Ix*Rx and you are good to go.
     
  3. KillerZ123

    Thread Starter New Member

    Nov 25, 2010
    7
    0
    OK I got it thanks for the help.
     
  4. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    Glad to hear you solved it.
     
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