A nonlinear capacitance cancellation technique and its application to a CMOS class AB power amplifier

A nonlinear cancellation technique is developed specifically for MOS Class AB power amplifiers. This technique utilizes a PMOS transistor at the amplifier input to cancel the variation of the input capacitance, thus improving the overall amplifier linearity. A monolithic CMOS RF power amplifier with this technique is designed and fabricated in a standard 0.6 mum CMOS technology. The prototype single-stage amplifier has a measured drain efficiency of 40% and a power gain of 7dB at 1.9GHz. Linearity measurements show that the new amplifier has over 10dB of IM3 improvement and 6dB of ACPR improvement compared with the traditional NMOS Class AB power amplifier.