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Homework Help: Output voltage of differential amplifier

  1. May 28, 2014 #1
    1. The problem statement, all variables and given/known data

    Find output voltage of differential amplifier having differential gain of 100 and common mode gain 0.1 if input voltages are v1=2+0.55sinwt and v2=0.5-0.005sinwt

    2. Relevant equations

    3. The attempt at a solution

    well, from sedra smith book i found the formula for output book

    v0= Ad(v1-v2)+Acm(v1+v2)/2

    if i have to subtract two AC signals with dc offsets i get v1-v2= 1.5+0.55sinwt am i correct?

    so can right it as 2.11sinwt
    again for Acm i have to take average of two signals which will be 1.25+0.272sinwt

    i have to divide it by 2 hence it becomes 1.522sinwt

    the final ans i am getting is 211.15sinwt am i correct?
  2. jcsd
  3. May 29, 2014 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Your sin term is off by about 1%.

    You don't divide the average by 2 again! And what happened to the dc term?

    the final ans i am getting is 211.15sinwt am i correct?[/QUOTE]

    Don't think so.
    Your starting formula is correct but then you seem to be floundering with the math.
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