Question

Draw a circuit diagram of a C.E. transistor amplifier. Briefly explain its working and write the expression for (i) current gain, (ii) voltage gian of the amplifier.

Answer 1

The purpose of this circuit is to amplify a small AC input signal, such as an audio or radio signal. A small AC voltage is applied to the input through a coupling capacitor. The ratio of the AC component of the output to the AC component of the input, is shown as gain.

(i) Current gain (also known as $\beta$-gain) = $\beta =\frac{\Delta i_c}{\Delta i_B}$

(ii) Voltage gain $\left(A_v\right)$ = Current gain $\times$ Resistance gain

or $A_v=\frac{\Delta i_C}{\Delta i_B}\times \frac{R_{out}}{R_{in}}$