Multi-mode WCDMA power amplifier module with improved low-power efficiency using stage-bypass

This paper presents a multi-mode power amplifier (PA) with very low DC quiescent current and current consumption under large power backoff operation. The PA is optimized to operate in three power modes. A dual-path PA is designed for high- and medium-power-mode operations, while a stage-bypass is applied to the final stage of the medium-power PA for low-power-mode operation. Load impedance for each power mode is individually optimized for best efficiency and linearity, achieving significant current saving compared to two-power-mode PAs. A 1.95GHz WCDMA PA module (PAM) has been developed using GaAs BiFET technology to validate the proposed circuit. The PAM demonstrates a very low quiescent current of 3.5mA under low-power-mode bias. The PAM exhibits 42% PAE and -40dBc ACLR1 at 28.5dBm Pout. At 17dBm and 8dBm backoff Pout, the PAM achieves 22% and 15% PAE, respectively, with -40dBc ACLR1. The current consumption at 8dBm Pout is reduced by 59% with the stage-bypass configuration.