Toroidal versus spiral inductors in multilayered technologies

This work is aimed to compare the performance of toroidal inductors and planar spiral inductors in multi-layered technologies. Toroidal inductors are investigated theoretically, and closed formula is derived for the inductance as a function of geometrical parameters. The obtained model is validated by experimental results and EM simulation. From the comparison of the inductance of toroidal inductors and compact spiral inductors, a selection rule is proposed to choose the most suitable topology that leads to the most compact design.