A Review of Hybrid Supply Modulators in CMOS Technologies for Envelope Tracking PAs

This article reviews trends, architectures, and recent developments in CMOS-based supply modulators (SM) used for envelope-tracking power amplifiers (ET-PAs). This review details the most commonly used hybrid supply modulator (HSM) architecture in CMOS and discusses its performance requirements and design challenges. The importance of efficiency, speed, linearity, and output power in HSM design is delineated and different methods that focus on maximizing these performance parameters are presented. Finally, the design challenges of envelope tracking systems are discussed, and an overview of device technologies for implementing SM and ET-PAs is given.