AC current gain( α AC) = ΔI c / ΔI e where ΔI c is change in collector current and ΔI e change in emitter current. AC voltage gain( A V) = Output voltage / Input voltage = α AC * Resistance gain = α AC * R o / R i
where R o is output resistance of the circuit and R i is input resistance of the circuit.
AC power gain = Change in output power / Change in input power
= AC voltage gain * AC current gain = α 2 AC * resistance gain
The input and output signals are in the same phase. There is no amplification in current of a given signal.
There is an amplification in voltage and power of the given signal. 2. In Common Emitter Amplifier
AC current gain(& beta AC) = ΔI c / ΔI e where ΔI c is change in collector current and ΔI e change in base current. AC voltage gain( A V) = & beta AC * resistance gain AC power gain =& beta 2 AC * Resistance gain