MOS varactor modeling with a subcircuit utilizing the BSIM3v3 model

This paper presents a subcircuit model for an MOS varactor based on the BSIM3v3 model suitable for simulator implementation within circuit-design environments. The development of the model and BSIM3v3 model parameter settings are discussed in detail. By varying the length (L) of the device, C/sub MAX//C/sub MIN/ ratios as high as five or minimum quality factors of 21.5 at 2.4 GHz can be achieved using a standard 0.35 /spl mu/m CMOS process. The investigation of different geometries resulted in a tradeoff between capacitance tuning and quality factor. A medium length varactor has been characterized.