Question 10.1: We wish to select appropriate values for the coupling capaci...
We wish to select appropriate values for the coupling capacitors CC1 and CC2 and the bypass capacitor CS for a CS amplifier for which RG = 4.7 MΩ, RD = RL = 15 kΩ, Rsig = 100 kΩ, RS = 10 kΩ, and gm = 1 mA/V. It is required to have fL at 100 Hz and that the nearest break frequency be at least a decade lower.
We select CS so that
f_{P2} = \frac{g_{m} + \frac{1}{R_{S}}}{2πC_{S}} = f_{L}
Thus,
C_{S} = \frac{1.1 × 10^{−3}}{2π × 100} = 1.75 μF
For fP1 = fP3 = 10 Hz, we obtain
10 = \frac{1}{2πC_{C1} (0.1 + 4.7) × 10^{6}}
which yields
CC1 = 3.3 nF
and
10 = \frac{1}{2πC_{C2} (15 + 15) × 10^{3}}
which results in
CC2 = 0.53 μF
Finally, we calculate the frequency of the zero fZ as
f_{Z} =\frac{1}{2πC_{S}R_{S}} = \frac{1}{2π × 1.75 × 10 ^{−6} × 10 × 10^{3}}
= 9.1 Hz