Modeling of current crowding for on-chip multi turn differential -spiral inductors

Current crowding severely degrades the quality factor (Q) of CMOS on-chip multi-turn spiral inductors. It needs to be considered in the lumped equivalent circuit models of inductors. Therefore its impact on RF circuit´s performance can be captured at circuit simulation phase. Such models have been established for multi-turn single-ended inductors. However they have not been well developed for differential inductors. In this paper, a wideband lumped equivalent circuit model for multi-turn differential inductors is proposed. It contains both resistance and inductance variations due to current crowding. The measurement results agree with the proposed model.