An Ultra-Compact, >17 dBm POUT, >30% PAE, Single Transformer-Based Doherty PA in 28-nm CMOS FD-SOI for 5G FR2 UE AiP Products

An ultra-compact Doherty power amplifier (PA), designed to operate across the n257, n258, and n261 bands for 5G FR2 user equipment (UE) with antenna-in-package (AiP) integration, is implemented in 28-nm CMOS FD-SOI technology. It is optimized for mobile applications, featuring a single amplifier-like footprint that enhances both efficiency and integration, and utilizes a staggered inter-stage matching network to compensate for the gain imbalance caused by the hybrid coupler. It also employs an adaptive bias circuit with a modified operational amplifier to enable wideband operation and achieve high efficiency in power back-off regions. The design is compact, relying solely on lumped components for implementation. The fabricated Doherty PA demonstrates output power above 17 dBm and power-added efficiency (PAE) of 30% when tested with 5G DFT-s QPSK modulation signals.