Question

Consider the circuit shown in the figure below:
The value of collector current and the value of $V_T=25mV$. If the value of collector current $I_c=1mA$ , then the value of voltage gain is.

• A. -20 V/V
• B. -40 V/V
• C. -10 V/V
• D. -100 V/V

Answer 1

The correct option is A -20 V/V

$\frac{V_0}{V_i}=-g_m{R}_C$
$\text{now,}{g}_m=\frac{\partial I_C}{\partial V_{BE}}=\frac{I_C}{2V_T}=\frac{1\times {10}^{-3}}{2\times 25\times {10}^{-3}}=20\text{mA/V}$
$\therefore \frac{V_0}{V_{in}}=-20\times {10}^{-3}\times 1\times {10}^3=-20V/V$