12 dBm OCP1dB Millimeter-wave 28 nm CMOS Power Amplifier using Integrated Transformers

Abstract

This paper describes the design of mm-wave integrated transformers and their application within a power amplifier (PA) in a 28 nm CMOS technology. The PA presents a 2-stage common-source differential topology and uses one transformer at the input and another at the output to perform single-ended to differential conversion, as well as another transformer to perform interstage matching. The baluns are sized to provide low insertion losses and high common-mode rejection rate (CMRR) as well as integrating the input and output matching networks. The designed baluns achieve minimum insertion losses better than 0.8 dB and CMRR superior to 27 dB. The output-stage transistors have a measured 1 dB output compression point (OCP1dB) of 10.2 dBm, 10.1 dB gain and peak power added efficiency (PAE) as high as 35%. Thanks to the transformers, the PA presents a compact implementation, occupying only 0.037 mm² on silicon. The fabricated PA achieves 12 dBm OCP1dB, 15.3 dB gain and peak PAE better than 20%.