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.