Power-added efficiency

Power-added efficiency (PAE) is a metric for rating the efficiency of a power amplifier that takes into account the effect of the gain of the amplifier. It is calculated (in percent) as:

${\displaystyle \mathrm {PAE} =100\times {\frac {P_{OUT}^{RF}-P_{IN}^{RF}}{P_{IN}^{DC}}}}$

It differs from most power efficiency descriptions calculated (in percent) as:

${\displaystyle \eta =100\times {P_{OUT}^{RF}}/{P_{IN}^{DC}}}$

PAE will be very similar to efficiency when the gain of the RF power amplifier is sufficiently high such that a low RF input power causes the RF power amplifier output to reach a certain level. But if the RF power amplifier gain is relatively low then the amount of RF input power that is needed to drive the RF power amplifier output to the certain level should be considered in a metric that measures the efficiency of the said power amplifier.