Note that all these definitions of power gains employ the use of average (as opposed to instantaneous) power quantities and therefore the term "average" is often suppressed, which can be confusing at occasions.
The operating power gain of a two-port network, GP, is defined as: where If the time-averaged input power depends on the load impedance, one must take the maximum of the ratio, not just the maximum of the numerator.
The transducer power gain of a two-port network, GT, is defined as:
where In terms of y-parameters this definition can be used to derive: where This result can be generalized to z, h, g and y-parameters as: where PS max may only be obtained from the source when the load impedance connected to it (i.e. the equivalent input impedance of the two-port network) is the complex conjugate of the source impedance, a consequence of the maximum power theorem.
The available power gain of a two-port network, GA, is defined as: