A three-mode switched-LNA has been developed using a 0.25 µm SiGe BiCMOS technology. The LNA features low noise figure (NF) performance, while achieving both low dissipation power and low distortion characteristics. The proposed MOSFET switch incorporating a newly developed switch circuit with a triple-well structure, which changes the LNA's mode, provides a parasitic capacitance of just 0.52 times that of a conventional MOSFET switch. This results in a significant NF improvement, by 0.16-0.33 dB, for the three-mode switched-LNA compared to a conventional LNA. Extensive studies of the MOSFET switch with regard to the structural parameters and the doping profiles are reported. Experimental results and the overall performance of a trial IC incorporating the three-mode switched-LNA are also given.