Gain The term Gain can be defined as the ratio of output to input  voltage  ( voltage gain ),  current  ( current gain ) or  electric power  ( power gain ). Gain is a unit of measurement i.e. the ratio of a signal output of a system to the signal input of the system. Gain is a term associated with  amplifiers . It is expressed using the  logarithmic   decibel  (dB) units (dB gain). Gain  is a proportion of the capacity of a  two-port   circuit  (often an  amplifier ) to increase the  power  or  amplitude  of a  signal  from the input to the output port   by adding energy converted from some  power supply  to the signal. Power Gain where , P denotes Power. Voltage Gain                                 where, V denotes Voltage,      ...