A 2.6-GHz-band 78-W Doherty power amplifier with GaN HEMT unit-cell structure robust for layout-dependent loop oscillation

Abstract

This paper proposes a unique unit cell structure of multi-finger GaN HEMT. The structure with a 360 um × 10 unit gate width cell is robust for layout-dependent loop oscillation inside the cell, and is well suited for delivering both high gain and high output power. Small-signal measurements show that the proposed cell exhibits 2 dB higher maximum available gain than a conventional cell. A packaged GaN HEMT based on the proposed cell delivers a 17.6 dB power gain, a 53.4 dBm output power, and a 66.5% drain efficiency at 2.6 GHz. To the best of authors' knowledge, the gain is the highest among single stage GaN HEMT amplifiers ever reported at the same output power range and the same frequency band. A Doherty power amplifier (DPA), which is fabricated with the two packaged GaN HEMTs, achieves a 14.9 dB high power gain, a 51.4% drain efficiency, a −50.3 dBc ACLR at a 48.9 dBm (78 W) average output power.