Ultra-Low Voltage Realization of the Tau-Cell and Its Application for Filtering Electrocardiogram Signals

A realization of the Tau-Cell using the concept of the Sinh-Domain filtering is introduced in this work. This is achieved through the employment of appropriate non-linear transconductor cells and grounded capacitors. Due to its companding nature and the employment of MOS transistors in the subthreshold region, the proposed topology is capable for operating in an ultra-low voltage environment, while the frequency characteristics of the derived filters could be electronically adjusted. In addition, its inherent class-AB nature allows the handling of signals with amplitude greater than the dc bias current. As a design example, a 2nd-order bandpass filter for deriving the Q, R, and S waves (QRS) complex of electrocardiogram (ECG) signal has been designed.