Design of a Fully Integrated Two-Stage Watt-Level Power Amplifier Using 28-nm CMOS Technology

We present a linear two-stage power amplifier (PA) for UMTS terrestrial radio access (UTRA) applications. The PA has been designed using a standard 28-nm complementary metal–oxide–semiconductor process. It includes an on-chip input matching network, a predriver stage, and an on-chip output matching network. Additional process-voltage-temperature compensation circuits and electrostatic discharge protection have been implemented on-chip. A differential triple-stack transistor array acts as transconductance circuit and generates watt-level RF output power. Measured saturated output power is more than 31 dBm and peak power-added efficiency is 33% for sinusoidal operation at 1.8 GHz. When applying memoryless digital predistortion (DPD) for 3rd Generation Partnership Project (3GPP) UTRA test vectors, an adjacent-channel leakage ratio of $leq -$33 dBc at $pm$5 MHz for 26.5-dBm output power is achieved. A corresponding error-vector magnitude of $leq$1.7% can be measured when using memoryless DPD.