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 rejecti
on ratio approaching 40dB. Moreover, the self-resonance frequency is t
wice that of a traditional grounded spiral of the same inductance valu
e, enabling higher reactances and Q-values to be achieved.