A reference design for a GaN-on-Si broadband Doherty power amplifier with a 6-W linear output power and greater than 35% efficiency at 2.5- to 2.7-GHz has been created by Nitronex and Prescient Wireless. The design, which uses Nitronex’s NPT25015 power transistor, provides a 10-dB gain with less than 2.0% error-vector magnitude with digital pre-distortion. Typical performance numbers were taken using a mobile WiMAX waveform defined as a single-carrier OFDMA 64-QAM 3/4 with a 10-MHz channel bandwidth. The 6-W output is achieved with a 9.5-dB peak-to-average power ratio at 0.01% probability on the complementary cumulative distortion function (CCDF) during the transmit portion of a 50% duty-cycle TTD signal.
The reference design consists of the schematic, bill of materials, circuit board layout files, detailed performance data, and documentation describing the design. Built and tested Doherty application boards are available for a suggested resale price of $1950. Reference design documentation and other information are available on the Nitronex Web site at http://www.nitronex.com. The companies are also collaborating on a reference design based on the Nitronex 125-W NPT25100. Preliminary results show similar performance specifications but at a much higher output power.