Voltage Gain of Emitter Follower
Fig. 1.11 shows the emitter follower circuit. Since the emitter
resistor is not bypassed by a capacitor, the a.c. equivalent circuit of emitter
follower will be as shown in Fig. 1.12. The ac resistance rE of the emitter
circuit is given by
In order to find the voltage gain of the
emitter follower, let us replace the transistor in Fig. 1.12 by its equivalent
circuit. The circuit then becomes as shown in Fig. 1.13. Note that input
voltage is applied across the ac resistance of the emitter circuit i.e., (r’e +
RE). Assuming the emitter diode to be ideal,
Output voltage, Vout = ie RE
Input voltage, Vin = ie (r’e + RE)
Voltage gain of emitter follower is
In most practical applications, RE
>> r’e so that Aν =1.
In practice, the voltage gain of an emitter
follower is between 0.8 and 0.999.
Related Topics
Privacy Policy, Terms and Conditions, DMCA Policy and Compliant
Copyright © 2018-2024 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.