Circuit models for PN integrated varactors

This paper compares different circuit models describing the performance of integrated varactors, which are designed, manufactured, measured and simulated with a 0.35 μm silicon standard technology. Three models are presented, named: simple, capacitive-inductive and physical. Their differences consist on the circuit elements used, capacitances, inductances and resistances, and the way they are connected. The more elaborated one, the physical model, contains a large number of components and, therefore, produces a better approximation of the varactor response. All models are accurate and scalable over a wide range of layout dimensions and can be used to design radio-frequency integrated circuits, RFICs.