A class-E power amplifier is proposed in this study. It uses both nMOS and pMOS as switching devices to reduce the voltage stress of each transistor. A voltage-combining scheme with nMOS and pMOS is proposed, and a transformer is designed using this scheme. The power amplifier is implemented in a 0.18-mu m RF CMOS process. Measurements show a maximum output power of 30.2 dBm with 36.8% power-added efficiency at a 3.3-V supply voltage. The power amplifier sustains a supply voltage of up to 3.9 V.