CMOS RF power amplifier with reconfigurable transformer

A CMOS RF power amplifier that can change the output transformer ratio is presented. The CMOS power amplifier is fully integrated in a 0.13 /spl mu/m process and has a power added efficiency (PAE) of 38% at 2.1 GHz and an output power of 30.7 dBm with 3.0 V supply voltage. The PAE at an output power of 16 dBm was increased by 40% by altering the transformer ratio.