NPN transistor is set up as amplifier in common emitter mode, output signal voltage obtained across the load resistance of 4 kΩ is 1 volt. Calculate input signal voltage. Assume current amplification fevelar = 250 and base resistance = 1 kΩ:

1 mV

The correct answer is option (3) : 1 mV

$I_C=\frac{V_C}{R_C}=\frac{1}{4\times 10^3}=0.25 mA$

$I_B=\frac{I_C}{B}=\frac{0.25\times 10^{-3}}{250}=10^{-6} A$

$V_i=I_BR_B$

$=10^{-6}\times 10^3=1\, mV$