As CMOS technologies scale, the transistor breakdown voltage decreases which complicates analog design. Critical circuits for power management and communication that must interface with outside voltage levels face daunting challenges. However, using conventional SOI CMOS, it is possible to design high voltage devices with no changes to the process flow which offer unique analog and microwave design opportunities. Silicon metal-semiconductor-field-effect-transistors (MESFETs) have been fabricated down to the 45nm SOI CMOS technology and show breakdown voltages greater than 25V. The devices have been shown to be robust and operate up to several Watts of power. This talk will describe methods for breakdown voltage enhancement, device characterization and circuit applications using the silicon MESFET device with a focus on power management and RF amplifiers.