The following formula shows how PAE is calculated.

This calculation requires the power usage of the DC supply and the input and output powers on the ports of the DUT. To see how different frequency and power levels affect PAE, you can make several measurements across a sweep of frequencies or power levels. The data collected helps identify the ideal operating range of the DUT.

Compression Point Measurement

The compression point is the power level at which the amplifier enters a saturation region where the output power does not grow in proportion to the input power. In this scenario the proportion constant is equal to the gain of the amplifier.

The most common compression points are the 1 dB, 2 dB, and 3 dB points (often written as P1dB, P2dB, and P3dB). Although a device's actual response will diverge from the theoretical response outside the linear range, P1dB is where the ideal linear response and measured data diverge by 1 dB.

The following graph shows an example of a PAE measurement with a compression point labeled.