Linearity of GaN HEMT RF power amplifiers - a circuit perspective

In this paper, the nonlinearity generation mechanisms causing AM/AM and AM/PM in GaN power amplifier are analyzed from a circuit perspective. The nonlinear device transconductance is found to be the primary source of slow compression in GaN PA's AM/AM characteristic, while the nonlinear input capacitance is the primary source of AM/PM distortion. Using two 800 MHz GaN PAs, we show that matching networks optimized for linearity can minimize a PA's nonlinear distortions and memory effects.