A 19 nW analogue CMOS log-domain 6th-order Bessel filter without E-minus cells

This paper contributes to the field of low-power high-order CMOS log-domain filters by: (a) suggesting a log-domain synthesis path which bypasses the need for E-minus cells and (b) by assessing the practicality of the proposed synthesis path by means of a 6th-order CMOS log-domain Bessel filter fabricated in the commercially available AMS 0.35 μm process. Measured results from the 19 nW, 8–200 Hz, 940 μm2 Bessel filter chip confirm the validity of the proposed approach. The filter reported here is particularly useful for biomedical instruments such as portable ECG devices and Pulse-oximeters.