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Homework Help: Amplifiers with feedback

  1. Apr 26, 2014 #1
    I have attached two different amplifiers with feedback, one of them is series-series amplifier and the second one is a shunt-shunt amplifier.

    Using the Hybrid-Pie transistor model
    • Determine the amplifier parameters Rin, Ro , Mid-band gain A
    • Determine the low cut-off (3-dB) frequency (Low-frequency Pole fL)
    • Determine the High cut-off (3-dB) frequency (High-frequency Pole fH)
    • Determine the Band Width (BW) and BW x Gain product.

    1. The problem statement, all variables and given/known data

    2. Relevant equations
    A = I_o / V_i
    B = V_f / I_o
    A_f = A / (1+BA)
    R_if = R_i * (1+BA)
    R_of = R_o * (1+BA)

    A = V_o / I_i
    B = I_f / V_o
    A_f = A / (1+BA)
    R_if = R_i / (1+BA)
    R_of = R_o / (1+BA)

    3. The attempt at a solution

    Attached Files:

    Last edited: Apr 26, 2014
  2. jcsd
  3. Apr 26, 2014 #2


    User Avatar

    Staff: Mentor

    Where is your attempt?
  4. Apr 26, 2014 #3
    i could only draw the ac circuit for the shunt-shunt amplifier with the feedback

    i already know the formulas for the shunt-shunt:
    A = V_o / I_i
    B = I_f / V_o
    A_f = A / (1+BA)
    R_if = R_i / (1+BA)
    R_of = R_o / (1+BA)

    But i don't know how to find V_o, I_i, I_f???

    Attached Files:

    • wo.jpg
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