10–82 By-Pass Capacitor Design In transistor amplifier design, a by-pass capacitor is connected across the emitter resistorRE to effectively short out the emitter resistor at signal frequencies. This design improves the gain of the transistor for the desired ac signals. The circuit in Figure P10–82

(a) is a common-emitter amplifier. The shaded portion is a low-frequency model of the transistor in use. In this problem, the task is to design a proper by-pass capacitor so that there is a pole at s = −300 rad=s. Reduce the circuit to its Thévenin equivalent as shown in Figure P10–82

(b) and then select the proper capacitor. RS =10 kΩ, Rπ = 2 kΩ,RE =3:3 kΩ, RL =1 kΩ, and β=70:

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www Rs iB(t) +1 Vs(t) RE Big(t) RL + vc(f) CE (a) ZT(S) ww + VT(S) VC($) -13 (b) FIGURE P10-82