By-Pass Capacitor Design In transistor amplifier design, a by-pass capacitor is connected across the emitter resistor RE to effectively short out the emitter resistor at signal frequencies. This then, improves the gain of the transistor for the desired ac signals. The circuit in Figure P10–70

(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 s¼300 rad/s. Reduce the circuit to itsThevenin equivalent as shown inFigureP10–70(b), and then select the proper capacitor. RS¼12 kV, Rp¼2.5 kV, RE ¼ 3.3 kV, RL ¼ 1kV, and b ¼ 50.

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1+ ww TiB (t) w Rs vs(t) R RE + BiB(t) RL vc(1) CE (a) ZT(s) +1 + VT(S) vc(s) (b) FIGURE P10-70 CES