A 2.6-GHz power amplifier was implemented with a 0.18 mu m RF CMOS process. The watching networks were fully integrated without any external components. To increase the output power, the power combining technique was adopted and realized by, a 2:1 on-chip transformer, which was designed to provide an optimum load for the power cell. The measured efficiency of this power combining transformer is about 7.5% at 2.6 GHz. The proposed power amplifier exhibits maximum output power of 26.7 dBm with power-added efficiency of 18.1%. The power gain is 13.6 dB under 3.3 V supply voltage. Moreover, this letter shows good agreement between simulated and measured results. (C) 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 299-302, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24910
