A Wideband Hybrid Envelope Tracking Supply Modulator with Slew-Rate-Enhanced Linear Amplifier

A wideband hybrid envelope tracking supply modulator (HETSM) with a slew-rate-enhanced linear amplifier (LA) is described in this work. The proposed slew-rate enhancement (SRE) structure introduces a parallel auxiliary current path directly to the gate of the class-AB output stage, significantly accelerating the charging and discharging processes of the Miller capacitor without modifying the operating point of the remaining LA. The current delivered via this supplementary path shows a rapid increase, with changes in input voltage, culminating in diminished quiescent current levels. The supply modulator is fabricated in a 180 nm CMOS process. The measurement results show that HETSM is able to track a 100 MHz, 16QAM signal accurately, achieving the maximum efficiency of 87.4% at a 5.12 W output power, with a load that consists of a 5 Omega resistor and a paralleled 100 pF capacitor. The proposed LA realizes a slew rate of -1857/+1239 V/mu s and a bandwidth of 226.6 MHz under a 24 mA quiescent current.