The Switched-Capacitor Power Amplifier: A Key Enabler for Future Communications Systems

In this paper, power amplifiers in CMOS technologies are reviewed including traditional PAs and the digital power amplifier (DPA). DPAs embed the functionality of an up-conversion mixer and digital-to-analog converter (DAC) in the PA. Hence a more appropriate label for DPAs is RF-Power-DACs. The "Switched-Capacitor Power Amplifier" (SCPA) is highlighted due to its potential to transform future communications networks because of its small-size, high linearity, and high efficiency. Because the SCPA (and other DPAs) can directly interface with digital signals while outputting RF signals, it is a flexible mixed-signal interface circuit that does not require a large baseband filter. Several recent innovations in the SCPA that enable it to be reconfigured digitally across multiple frequency bands and to be used in beamforming/MIMO transceivers are highlighted.