A pHEMT power amplfier with an on-off modulator

This paper presents a transformer-based switching-type RF power amplifier with an on-off modulator using a 0.15-μm pHEMT process. In order to overcome the inherent limitation of ground potential at the source node of transistor models in this pHEMT process, an on-off modulator was designed for the proposed pulse-modulated polar transmitter system. Measurement using a single-tone signal at 2.2 GHz and a 3.8-V supply, this pHEMT power amplifier with the proposed on-off modulator under full turn-on condition achieves 50.1% efficiency at 26.7-dBm output power level. Moreover, it achieves 45.3% efficiency at 23.7-dBm output power level under the half turn-on condition. Furthermore, the isolation of this system at the peak output power level under full turn-off condition is 23.3 dB which is much better than using gate bias control to switch the cell of power transistors.