Monolithic Class E SiGe Power Amplifier Design with Wideband High-Efficiency and Linearity

Abstract

This paper discusses and compares the design of monolithic RF broadband class E SiGe power amplifiers (PAs) centered at 900MHz that are highly efficient and linear. It is found that high power-added-efficiency (~65%) can be achieved with PAs designed using either high-breakdown or high-fT SiGe transistors. The PAs designed with high-breakdown devices can provide ~3% better efficiency at higher supply voltages but with worse bias sensitivity, inferior broadband frequency response, and slightly lower gain than those designed with high-fT devices. However, the class E PAs designed using high-breakdown devices can be successfully linearized using an open-loop envelope tracking (ET) technique as their output spectra pass the stringent EDGE transmit mask with margins, achieving an overall system PAE of 44.4% that surpasses the ~30% PAE obtainable using commercial GaAs class AB PAs. These promising results indicate the feasibility of realizing true single-chip wireless transceivers with on-chip RF SiGe PAs for spectrally-efficient non-constant-envelope modulation schemes