Centre-tapped spiral inductors for monolithic bandpassfilters

Abstract

A centre-tapped spiral inductor is proposed for use in fully balanced monolithic bandpass filters. The design consumes only 63% of the area required by two traditional spirals and delivers a common-mode rejection ratio approaching 40 dB. Moreover, the self-resonance frequency is twice that of a traditional grounded spiral of the same inductance value, enabling higher reactances and Q-values to be achieved.