A number of different CMOS implementations of power amplifiers (PAs) have performed well [1-4], but most of them are switching-type PAs. In this paper, we report the first demonstration of a single-chip linear CMOS PA for OFDM WLAN applications. This PA adopts a fully differential topology with a transformer- type output matching and operates at VDD = 3.3V. All of the components are integrated on a single 0.18μm CMOS die, including input balun and output transformer, and no off-chip components are required.