Doping profiles for optimum class B performance of GaAs MESFET amplifiers

The doping profiles and matching circuit conditions for maximum power added efficiency of GaAs MESFET amplifiers are investigated. A large signal MESFET model is used to simultaneously optimize doping and circuit parameters. Efficiency is found to be most sensitive to the breakdown voltage of the MESFET, which can be improved by reducing I/sub dss/, lowering the surface doping concentration, and allowing the peak doping region to be deeper in the channel. High efficiency cannot be obtained without proper harmonic tuning at both the load and generator side of the MESFET. Second harmonic impedances at the generator and load must be minimized. The third harmonic impedance at the generator and load should be maximized while the fundamental impedances should be selected to conjugately match the device.<>