Design and realisation of a 50 W GaN class-E power amplifier

Modern wireless systems demand increasing performance from power amplifiers (PAs) in terms of output power and efficiency. Due to the large number of transistor fingers used in such applications, distributed effects have to be taken into account when designing circuits for high-power applications. In this paper, a 50 W class-E power amplifier is designed based on a GaN HEMT powerbar. The performance degradation due to impedance mismatch between the different unit cells of the powerbar is studied. Techniques to reduce the impairments are analysed in simulations and verified through a hybrid design. The final design employs two ribbon bonds glued together at gate and drain of each transistor cell as well as a short notch in the centre of the transmission lines leading to and from the powerbar. These measures reduce the distributed effects and result in an efficient amplifier design. Measurement results on switching-mode PA using a GaN powerbar with a gate width of 9.6 mm show peak drain efficiency η and PAE of 74.3 % and 71.6 %, respectively, for an output power of 43.3 dBm at 2.42 GHz when operated from a 30 V supply.