Question

In a $CE$ transistor amplifier, the audio signal voltage across the collector resistance of $2 \, k\Omega $ is $2 \, V$ , if the base resistance is $1 \, k\Omega $ and the current amplification of the transistor is $100$ then the input signal voltage is

• A. $10mV$
• B. $1mV$
• C. $0.1V$
• D. $1V$

Answer 1

Answer: (A)

Current amplification factor,
$\beta =\frac{\Delta I_{C}}{\Delta I_{B}}$
Collector current,
$\Delta I_{C}=\frac{2 V}{2 \times 10^{3} \Omega}=1\times 10^{- 3}A$
Base current,
$\Delta I_{B}=\frac{V_{B}}{R_{B}}=\frac{V_{B}}{1 \times 10^{3}}=V_{B}\times 10^{- 3}$
Given, $\beta =100$
Now, $100=\frac{10^{- 3}}{V_{B} \times 10^{- 3}}$
$\Rightarrow V_{B}=\frac{1}{100}V=10mV$