Question

for a common emitter amplifier, the audio voltage across the collector is 1kohm voltage developed is 3v. if current amplification factor is50,find the input signal voltage and base current if the base resistance is 10kohm.

Answer 1

voltage across collector resistance of 1 k ohms = 3 V
collector current I = 3/1000  = 3 milli amp

current amplification factor = Beta dc = 50
So base current =  collector current / Beta  = 3 / 50 milli amp = 60 Micro Amp

Voltage drop across the base resistance = 10 k ohm * 60 *10^-6 Amp
         = 0.6 Volts
Voltage across base and emitter = 0.7 volts
Voltage of input signal =  0.6 + 0.7 volts = 1.3 volts