A Fundamental Approach for Design and Optimization of a Spiral Inductor

This technical paper presents a fundamental approach for design and optimization of a spiral inductor using ASITIC (analysis and simulation of spiral inductors and transformers for ICs) and SpiralCalc (integrated spiral inductor calculator). Both tools are available for research and non-commercial purposes. Inductors are key components esp. for impedance matching and are designed such that they would exhibit a high Q-factor (quality-factor) for the specific inductance and frequency range of operation. A sample value of 5.3 nH is set for this paper for the spiral inductor design using the tools. For optimum Q-factor, an octagonal geometry for spiral inductor is used for ASITIC design, to have a close comparison to that of the SpiralCalc. Design methodologies for the optimization of the spiral inductor parameters such as the inductance and the Q-factor are discussed. Results comparison between the two tools is also presented. Design tradeoffs between inductor parameters are inevitable, and these parameters affect the performance of the inductor esp. at higher frequencies. With this, it is crucial that inductors be designed carefully for their effective frequency range of operation and specific requirements of the intended application.