A 500-nA sixth-order bandpass SC filter

A sixth-order bandpass switched-capacitor (SC) filter that requires only 500 nA of total supply current has been designed and fabricated in a 2-μm CMOS technology. The filter is part of an implantable device powered by a ±1.2-V battery; it can drive up to 30 pF of capacitive load and uses a 2-kHz sampling frequency. A substantial reduction in the power consumption has been achieved by using a novel amplifier time-sharing technique that allows the realization of an arbitrary number of biquadratic cells with only two amplifiers. Further power saving was obtained with the use of positive feedback in the amplifier input stage to enhance its transconductance. The prototype chip requires an area of 2200 mils