Prove that in a common-emitter amplifier, the output and input differ in phase by . In a transistor, the change of base current by 30 produces change of 0·02 V in the base-emitter voltage and a change of 4 mA in the collector current. Calculate the current amplification factor and the load resistance used, if the voltage gain of the amplifier is 400.
Let us consider that input signals,
and the output signal,
The voltage amplification,
Since,
here negative sign indicated that output is out of phase with respect to the input signal.
Now, calculating the Amplification factor
Hence,
Now, calculating the lead resistance