A CMOS power amplifier using split input and output transformers to minimize its chip area

Abstract

In this study, we propose a layout technique to reduce the chip area of differential RF CMOS power amplifiers in which input and output transformers are utilized as input and output baluns. To minimize the chip area of the CMOS power amplifier, we split a conventional spiral transformer into two identical parts, thereby making full use of the wasted area in the conventional power amplifier. Using the proposed split transformers in the input and output transformers, we successfully reduce the chip area of the CMOS power amplifier based on a differential structure. To verify the feasibility of the proposed split cascode structure, we designed a 2.4-GHz CMOS power amplifier using a 180-nm SOI RF CMOS process. With an IEEE 802.11n WLAN modulated signal, we obtain a maximum output power of 9.73 dBm. From the measured results, we verify the feasibility of the proposed split transformer structure for RF CMOS power amplifier applications. (c) 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1443-1446, 2016