Accumulation MOS varactors for 4 to 40 GHz VCOs in SOI CMOS

It has recently been shown that MOS capacitors fabricated in deep submicron CMOS technologies can serve as high-Q varactors for RF circuit design. The devices are often operated with the silicon surface in accumulation to maximize Q, and so have been termed accumulation mode or AMOS varactors. This paper combines MEDICI simulation and experimental results to demonstrate that AMOS varactors fabricated in SOI technology can provide significant advantages over bulk technology devices at the same channel length. A low voltage AMOS varactor with wide tuning range and high Q fabricated in a 0.13 μm CMOS technology is reported. The varactors have been employed in VCO circuits operating at frequencies in excess of 40 GHz.