Electronic Circuit Analysis

8 Electronic Circuit Analysis
1.3.5 Power Gain
As RL increases, A~~decreases. As RL increases, Ay also increases.
Therefore, Power Gain which is the product of the two, Ay and AI varies as shown in Fig. 1.8.
Ap=AyAI
t
--+ ~
Fig. 1.8 Variation of Ap with RL
Power Gain is maximum when RL is in the range 100 KQ - 1 MQ i.e., when RL is equal to the
output resistance of the transistor. Maximum power will be delivered, under such conditions.
Therefore, it can be summarised as, Common Emitter Transistor Amplifier Circuit
will have, .
1. Low to Moderate Input Resistance (300£2- 5KQ).
') Moderately High Output Resistance (10K£2- 100KQ).
3. Large Current Amplification.
4. Large Vo:tage Amplification.
5. Large Power Gain.
6. 180 0 phase-shift between input and output voltages.
As the input current I B
, increases, Ie increases therefore drop across Re increases and
V o = Vee - VI drop across Rc- Therefore, there is a phase shift of 180°.
The amplifier circuit is shown in Fig. 1.9.
Fig. 1.9 CE Amplifier Circuit