GaN MMIC broadband Doherty power amplifier

A quarter-wavelength transformer, phase compensation network, offset line are the bandwidth limiting factors of Doherty PAs. In this paper, we expand the bandwidth of the Doherty PA by employing a new structure. The conventional phase compensation network is merged into an input matching circuit and the offset line is resonated-out by an inductor. The quarter wavelength transformer has a low-Q characteristic compared to that of conventional one. With the proposed topology, a broadband Doherty PA is implemented using TriQuint 3MI 0.25μm GaN-HEMT MMIC process. Across 2.1-2.7 GHz, the implemented PA delivered a DE of over 40.5%, a gain of over 11.8 dB and ACPR of below -45dBc at an average power of over 33.2 dBm for LTE signal with a 6.5 dB peak-to-average power ratio. This fully integrated circuit has a chip-size of 3.5mm by 1.9mm.