Gain: Changed meanings for compressed amplifiers

With intentional compressed amplifier operation to achieve higher energy efficiencies, it is constructive to revisit the concept of amplifier gain because when an amplifier operates in compression the output signal is no longer directly proportional to the input signal. Two approaches to the concept of gain, slope-gain and ratiometric gain, are examined in this nonlinear regime. These measures are shown to match at small signal levels and diverge as amplifier compression increases. Slope-gain characteristics relate directly to output waveform distortion, and hence to amplifier linearizer design. Gain measured by power differenced in dB, widely used in RF engineering standard practice, is shown to be a ratiometric measure and not directly applicable to linearizer design.