Question

For a CE-transistor amplifier, the audio signal voltage across the collected resistance of 2 kΩ is 2 V. Suppose the current amplification factor of the transistor is 100, find the input signal voltage and base current, if the base resistance is 1 kΩ.

Answer 1

Collector resistance, RC = 2 kΩ = 2000 Ω
Audio signal voltage across the collector resistance, V = 2 V
Current amplification factor of the transistor, β = 100
Base resistance, RB = 1 kΩ = 1000 Ω
Input signal voltage = Vi
Base current = IB
We have the amplification relation as:
Voltage amplification =$\frac{ V}{V_i} =β\frac{R_c}{R_b}$
Vi = $\frac{V}{β}$ $\frac{R_B}{R_C}$
Vi = $\frac{2\times 1000}{100\times 2000}$
Vi = 0.01 V
Therefore, the input signal voltage of the amplifier is 0.01 V.
Base resistance is given by the relation:
RB =$\frac{V_i}{I_B}$
RB = $\frac{0.01}{1000}$
RB = $10\times10^{-6} A$
RB = 10$μA$
Therefore, the base current of the amplifier is 10 $µA$.