Dynamically Load Modulated Power Amplifier Using Transistor Source Impedance Variation

Abstract

This work presents a novel dynamic load modulation (DLM) power amplifier that does not require an input power splitter. The load is modulated using an auxiliary transistor's source impedance variation with output power. A proof of concept circuit is designed and simulated in a 65 nm TSMC CMOS technology. The transconductance (gm) of the auxiliary transistor is used as the PA's load modulator. Operating from 2.3-2.5 GHz, the DLM PA demonstrates an output power of 10.4 dBm at 2.5 dB compression and a maximum gain of about 20 dB. The PA's power added efficiency (PAE) is 27% at the peak power and 20% at 6 dB output power back off. Output power combining is realized using an unequal lumped-element Wilkinson power combiner. The presented DLM PA has compact size because it does not require an input power splitter.