• Doherty power amplifier;
  • efficiency;
  • driving amplifier;
  • GaN HEMT;
  • power tracking


This letter represents a three-stage Doherty power amplifier with a bias controller.The driving amplifier controls the input power of the carrier cell to eliminate the gate current of the carrier cell at high input power levels. The gate bias voltage of the driving amplifier is controlled by a power tracking method according to input power levels. For verifications, the driving amplifier, carrier, and peaking cells are fabricated using 10-W, 15-W, 35-W gallium nitride high electron mobility transistors, respectively, at 3.5 GHz. From a continuous wave, the power-added efficiencies (PAEs) of 34.4 and 39.6% are achieved at ∼9.5- and 4.3-dB back-off powers, respectively. For a worldwide interoperability for microwave access signal, the proposed DPA has the PAE of 37.1 % at an output power of 41.5 dBm. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:23–26, 2012; View this article online at DOI 10.1002/mop.26474