An Inductive-Neutralized 26-dBm $K$ -/ $K_{a}$ -Band Power Amplifier With 34% PAE in 90-nm CMOS

This article presents a fully integrated K-/K_a-band transformer-combined power amplifier (PA) with a novel inductive neutralization technique implemented in the 90-nm CMOS process for fifth-generation and 24-GHz industrial scientific and medical-band applications. Four single-stage cascode cells are combined with transformers as two differential amplifier cells. The current-combining topology is used to combine the two differential amplifier cells to increase the output power. The asymmetrical transformers are designed to compensate the phase imbalance. The novel inductive neutralization structure together with the capacitive neutralization is used to resolve the overall stability issue without output power degradation. The measurement results demonstrate 16.3-dB small-signal gain, saturated power (P_sat) of 26.0 dBm, output 1-dB compression point (OP_1dB) of 23.2 dBm, and peak-added efficiency (PAE) of 34% at 28 GHz. The chip size with all pads is 0.401 mm². To the authors' knowledge, this circuit demonstrates a superior output power and PAE performance compared with the reported K-/K_a-band CMOS PAs.