This paper describes the development of a high-voltage transistor in a standard 0.35 ?m CMOS technology and its application on a class E power amplifier for mobile communications. The use of a higher voltage already available in the battery has the benefit of reducing the electromigration constrains and having lower voltage drops in the interconnects due to the use of a lower current. Measured results on the active device and simulation show that is possible to achieve a higher power added efficiency using a lateral double diffused MOS, while reducing the current draining the battery.