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

Updated On: Apr 20, 2025

10 mV
20 mV
30 mV
15 mV

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The Correct Option is B

Solution and Explanation

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.

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Concepts Used:

Semiconductors

Semiconductors are a crystalline solid materials, whose electrical conductivity lies between a conductor and an insulator. Semiconductors are mainly used in the manufacturing of electronic devices like capacitors, transistors, diodes, Integrated circuits, etc.

Properties of Semiconductor:

Semiconductor acts like an insulator at Zero Kelvin. On increasing the temperature, it works as a conductor.
Due to their exceptional electrical properties, semiconductors can be modified by doping to make semiconductor devices suitable for energy conversion, switches, and amplifiers.
Lesser power losses.

Uses of Semiconductor:

Semiconductors are widely used in manufacturing electronics devices like transistors, diodes, sensors, integrated circuits.
Semiconductors are widely used in all electronic devices, like mobile phones, digital cameras, communication devices, trains, ATMs, etc.