Question

Power gain for the transistor as an amplifier can be given by:

• A. ${\beta }^2\times$ Resistance gain
• B. $\beta \times$ Resistance gain
• C. ${\beta }^2\times$ Current gain
• D. ${\beta }^3\times$ Current gain

Answer 1

The correct option is A ${\beta }^2\times$ Resistance gain

Power gain = $\frac{smallchangeinoutputpower}{smallchangeinninputpower}=\frac{\Delta P_o}{\Delta P_i}$
$P_o=V_o{I}_C=I_C^2{R}_o$
$\therefore P_o=\Delta I_C^2{R}_o$
$P_i=V_i{I}_B=I_B^2{R}_i$
$\therefore P_o=\Delta I_B^2{R}_i$
Power gain $=\frac{\Delta I_C^2{R}_o}{\Delta I_B^2{R}_i}={\left(\frac{\Delta I_C}{\Delta I_B}\right)}^2\times \frac{R_o}{R_i}$
$={\beta }^2\times$ resistance gain