Question

A transistor has a current amplification factor (current gain) of $50$. In a common emitter amplifier circuit, the collector resistance is chosen as $5\,\Omega$ and the input resistance is $1 \,\Omega$. The output voltage if input voltage is $0.01\, V$ is

• A. $-2\, V$
• B. $-5 \,V$
• C. $-2.5\, V$
• D. $- 1\, V$

Answer 1

Answer: (C)

The voltage gain of a common emitter amplifier
$A_v = - \frac{\beta R_0}{R_i}$or
$\frac{V_0}{V_i} = - \frac{\beta R_C}{R_B}$
Output voltage,
$\therefore V_0 = -\frac{\beta R_C V_i}{R_B}$
$= -\frac{50\times 5\times 0.01}{1}$
$= - 2.5\,V$