An equivalent circuit model for on-chip inductors with gradual changed structure

Inductor with gradual changed metal width and space by good design can get better Q factor than the inductor with fixed metal width and space. In this paper, a simple wide-band inductor model is presented considering both the increase of resistance and the decrease of inductance due to the skin and proximity effects. This model has been verified with simulation and the experimental results of spiral inductors with various geometrical configurations on high-resistivity silicon substrate. Good agreements have been achieved under the selfresonance frequency, which indicates its accuracy. This model has also been proved to be suitable for both the conventional inductor with fixed structure and the inductor with gradual changed structure.