Elimantation

Discussion in 'Math' started by Steve1992, Sep 8, 2012.

  1. Steve1992

    Thread Starter Senior Member

    Apr 7, 2006
    100
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    Vc - Vo = I1Rf

    Vcc - Vc = (I1 + I2)R1 (2)

    Vc-(-Vcc) = Vc + Vcc = I2R2

    Elimate I1 and I2 from the above equation and show that:

    Vcc - Vc = (Vc - Vo)R1/Rf + (Vc + Vcc)R1/R2


    I understand that I1 and I2 are replaced from (2) with (Vc - Vo) and (Vc + Vcc) but how does /Rf and /R2 slot in?

    Thanks
     
  2. panic mode

    Senior Member

    Oct 10, 2011
    1,321
    304
    you have I1 in

    Vc - Vo = I1Rf

    which can be expressed as

    I1=(Vc - Vo)/Rf

    same should apply for getting I2 from some other equation like
    Vc + Vcc = I2R2

    I2=(Vc + Vcc)/R2

    then you replace I1 and I2 in (2) to get result
     
    Steve1992 likes this.
  3. WBahn

    Moderator

    Mar 31, 2012
    17,777
    4,804
    I don't think you do understand it, because it isn't true. I1 and I2 are currents while (Vc-Vo) and (Vc+Vcc) are voltages; you can't just replace one with the other. Hopefully panic mode's suggestion has cleared things up for you.