A Single-Chip Variable Supply Voltage Power Amplifier

A single-chip implementation of a variable supply voltage power amplifier (PA) is presented. The circuit is design in SiGe BiCMOS technology and is composed of a differential power amplifier designed for WCDMA operation and a "buck" DC-DC converter. The combined system varies the supply voltage of the PA from 2.7V to 1.2V and maintains system linearity while the output power is not at its maximum. The system achieves an average battery current reduction of 30% and an average efficiency improvement of 46% compared to a fixed supply voltage approach, while occupying a 2mm x 2.5min die area.