# Amplifiers with feedback

1. Apr 26, 2014

### jafferrox

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

AC-Analysis:
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
ٍseries-series:
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)

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)

3. The attempt at a solution

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• ###### ssamplifier.png
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Last edited: Apr 26, 2014
2. Apr 26, 2014

### Staff: Mentor

3. Apr 26, 2014

### jafferrox

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???

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