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#### A 32.3dBm Quadrature Complex Domain Doherty Power Amplifier Based on Switched Constant-Current and Symmetrical Transformer Achieving 21.6% Average Power-Added Efficiency

This paper presents a power-efficient quadrature switched constant-current power amplifier (PA) based on IQ sharing. This PA, combining the complex domain Doherty and a symmetrical transformer that absorbs a λ/4 impedance converter, can generate four power efficiency peaks to significantly improve the power-added efficiency (PAE) at the PA’s power back-offs (PBOs). Fabricated in a 28 nm CMOS process, the PA achieves a peak output power (Pout) of 32.3 dBm and a peak PAE of 37% at a 2 GHz carrier. The PAEs at 3-, 6-, and 9-dB PBOs are 35.7%, 25.1%, and 23.7%, respectively. When testing an LTE 20-MHz 256-QAM signal with 5.8-dB PAPR, this PA achieves an average Pout of 26.5 dBm, an average PAE of 21.6%, -31.2 dB EVM, and -32.5/-32.3 dBc ACLR.