An average power tracking (APT) Doherty power amplifier (PA) is analyzed in terms of its biasing voltage condition, efficiency, and output power. And the drain and gate bias voltages are optimized for operation at different output power conditions. The Doherty power amplifier is designed using 45 W gallium nitride (GaN) high electron mobility transistors (HEMT) for the carrier and peaking cells at 1.94 GHz. The bias voltages are controlled for each average power level(42.9 dBm, 39.9 dBm, 37 dBm). The measured drain efficiencies and gains are 53.2%, 12.8 dB at 42.9 dBm and 54.3%, 11.2 dB at 39.9 dBm and 53.4%, 9.1 dB at 37 dBm for a 10 MHz LTE signal with a 6.5 dB PAPR. This result demonstrates that the Doherty PA can be reconfigured for different average output powers using the bias voltage control method.