In this paper, we describe the development of a single chain dual band power amplifier for GSM900/1800 applications. RFIC features include: single input-single output topology, three stages of amplification switched input and inter-stage matching, positive power control, and negative voltage generation. The chip is fabricated using a high volume ion-implanted 0.5 mu m GaAs MESFET process and is assembled in a tow cost, thermally enhanced SSOP16 plastic package. Typical performance, at +4.8 Volts in GSM and DCS bands, is 48% PAE at Pout = +35 dBm and 44% PAE at Pout = +32.5 dBm respectively.