MESFET devices provide high breakdown characteristics, enable high voltage operation, and direct battery hook-up with no changes in processing on state of the art SOI and SOS CMOS processes. Fundamental analog building blocks, including single-ended and differential amplifiers and high impedance current mirror were designed and fabricated in a single poly, 3-layer metal digital CMOS technology utilizing fully depletion mode MESFET devices. The measured breakdown voltage of the SOS MESFETS presented here has a breakdown voltage of over 7.5 V without causing irreversible damage. DC characteristics were measured by varying the power supply from 2.5 to 5.5V. The measured DC transfer curves of amplifiers show good agreement with the simulated ones with extracted models from the same process. The accuracy of the current mirror showing inverse operation is within ±5% for the current from 0 to 1.5 mA with the power supply from 2.5 to 5.5V.