High Speed and High Efficiency GaN Envelope Amplifier with Source-Floating Half-Bridge Switch

This paper presents a high speed and high efficiency GaN Envelope Amplifier (EA) for Envelope Tracking Power Amplifier (ETPA) application. The proposed EA consists of series inductor, low pass filter, single half-bridge switch using depletion-mode 0.15um GaN HEMT with source-floating and its driver circuit. In ETP A applications, envelope signals are de-troughed in order not to operate the P A with extremely low gain, and therefore it is possible to generate the same envelope signal from the half-bridge switch with source-floating as that with source-grounding by proper signal processing. This structure leads to high efficiency and linearity of the EA, and reduces the complexity of the driver-circuit. The designed and fabricated envelope amplifier with proposed structure achieved total efficiency of87.8%and NRMSE of 2.8% under 20MHz modulation signal, and PAE of 77.7%, and NRMSE of 4.9% under 80MHz modulation signal with switching frequency of 184MHz and 400MHz respectively.