Abstract: “The continuous varactor is an adjustable storage element often used in filter, resonant and delay control circuit. This paper presents the method to implement linear integrated continuous varactor. Through driving several MOS capacitors into inversion-mode (IMOS) with different bias, various characteristics arise in the capacitance with respect to overdrive voltage. The IMOS with various capacitances can be further utilized to synthesize a wide range linear varactor. By using TSMC 0.35um CMOS process, the implemented varactorprovides ±33% tunable capacitance within ±12% tuning range of voltage. In addition, the integrated varactor reaches picofarad scale which is considerably practical in many applications.”

Keywords: varactor, resonant circuit, inversion mode, IMOS, tuning range.