Question

Voltage gain for a transistor as an amplifier for CE configuration is given by:

• A. $A_V={\beta }^2\times$ Resistance gain
• B. $A_V=\beta \times$Current gain
• C. $A_V=\beta \times$ Resistance gain
• D. $A_V={\beta }^2\times$ Current gain

Answer 1

The correct option is C $A_V=\beta \times$ Resistance gain

Voltage gain is defined as ratio of small change in the output voltage to the small change in the input voltage when transistor acts in the mid of active region.
i.e, $A_V=\frac{\Delta V_o}{\Delta V_i}$
$\Delta V_o=\Delta V_{CC}-I_C{R}_L$
$\Delta V_i=\Delta V_{BE}+I_B{R}_B$
$\therefore V_o=\Delta I_C{R}_L$
$\therefore V_i=\Delta I_B{R}_B$
$\left|A_V\right|=\left(\frac{\Delta I_C}{\Delta I_B}\right)\left(\frac{R_L}{R_B}\right)$
$=\beta \times$ resistance gain.