This paper describes the design of a push-pull power amplifier (PA) with a center-tapped transformer for transmitter applications on the 5.2-GHz band using 0.18m CMOS technology. The type of the proposed PA is based on a double-ended push-pull (DEPP) configuration. DEPP has a simple construction with only transistors and transformers. The PA has reverse-phased cascode-connected transistors. The proposed transformer has a multilayer structure and was designed using electromagnetic field simulation. To achieve high power added efficiency (PAE), we assumed the optimized output impedance technique with a tunable impedance antenna. The PA has 13.2 dB linearity gain, 14.9 dBm 1-dB compression point (P1dB), and 27.4% maximum PAE. (c) 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.