Question

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

• A. 10 mV
• B. 20 mV
• C. 30 mV
• D. 15 mV

Answer 1

The Correct Option is B

Voltage Gain Calculation 

Given values:

• \(\beta = 100\)
• \(R_C = 2 \, k \Omega\)
• \(v_0 = 4 \, V\)
• \(R_B = 1 \, k \Omega\)

The voltage gain (A) is given by:

\(A = \frac{v_0}{v_i} = \beta \frac{R_C}{R_B}\)

Now, solving for input voltage \(v_i\)

\(v_i = \frac{v_0 \times R_B}{\beta R_C}\)

Substitute the given values:

\(v_i = \frac{4 \times 10}{100 \times 2 \times 10^3} = 20 \, mV\)

Conclusion:

The input voltage \(v_i\) is 20 mV.