A 0.5 V Low Power DTMOS OTA-C Filter for ECG Sensing Applications

Abstract

This paper presents a 0.5 V ultra-low power Gm - C fourth order low pass filter with Butterworth response for ECG detection. An Operational Transconductance Amplifier (OTA) forms the basic building block of the filter. In order to achieve high performance at low power, the G m cell has been designed using Dynamic Threshold MOS (DTMOS) in 180 nm CMOS N-well technology. A hybrid design that uses a DTMOS pseudo differential architecture with G m reduction enables the OTA to operate at 0.5 V achieving a transconductance as low as 0.25 nS, which cuts down the area of large on-chip capacitance significantly for low frequency applications. The designed filter has a cutoff frequency of 7.3 Hz with a total power consumption of 29.7 nW. The simulated variation of the achieved cutoff frequency over the process corners is less than ± 10 %.