Question

For CE transistor amplifier, the audio signal voltage across the collector resistance of $2k\Omega$ is $4V$. If the current amplification factor of the transistor is $100$ and the base resistance is $1k\Omega$, then the input signal voltage is

• A. $5mV$
• B. $10mV$
• C. $20mV$
• D. $30mV$

Answer 1

The correct option is C $20mV$

Given that:
$\frac{I_{\alpha }}{I_{\beta }}=100;R_C=1000\Omega$, $V_0=4V$
So, $\beta =\frac{I_{\alpha }}{I_{\beta }}=100$
$\Rightarrow V_{gain}=\frac{V_0}{V_i}=\beta \frac{R_L}{R_C}$
$\Rightarrow V_i=\frac{4\times 1000}{100\times 2000}=0.02V$$=20mV$