Broadband digitally-controlled power amplifier based on CMOS / GaN combination

A multiWatt RF power amplifier operating in the frequency range 0.5 to 1.2 GHz is reported, whose output amplitude is determined by digital input words (“RF Power DAC operation”). The amplifier employs a CMOS IC for digital control, directly connected to a GaN FET operating in common-gate mode. The use of the GaN FET allows power supply voltages in excess of 15 V to be used. A load resistance of 50 ohms can be directly connected to the GaN FET, thereby avoiding bandwidth limitations from output matching networks. Output power in the range 2 to 3 W and drain efficiencies above 50% are obtained over more than an octave of bandwidth.