Over 65% PAE GaN voltage-mode class d power amplifier for 465 MHz operation using bootstrap drive

We report a digitally-driven switching-mode amplifier using GaN devices in Voltage-Mode Class D operation, for use at 465 MHz (the recently designated frequency for LTE Band 31). The amplifier is fabricated as an integrated circuit including output devices and drivers. The output circuit employs two stacked GaN FETs; a bootstrap-drive configuration is used in order to increase the driver-stage efficiency for the uppermost GaN FET. The GaN VMCD amplifier achieves peak power-added efficiency of 66.6%, and an output power of 3.3W. At 6dB power backoff, power-added efficiency of 36.3% is achieved. These power-added efficiency values are the highest for reported GaN VMCD amplifiers at a commercial wireless frequency.