A Low-Power Current-Mode Analog QRS-Detection Circuit for Wearable ECG Sensors

In this paper an ultra-low power current-mode analog circuit is proposed for detecting QRS complexes from the ECG signal. An accurate low-power operation is obtained by using a non-linear energy operator and designing all the transistors in subthreshold region. For improving the performance of the circuit, three filters with very-low cutoff frequencies are utilized which do not require large capacitors and so do not occupy large area. Two of the three filters are used for realizing onset detection method and the other is used for estimating a threshold which is required for QRS detection. Simulating over the entire MIT/BIH arrhythmia database shows the acceptable values of 98.69% for the average accuracy, 99.24% for the sensitivity and 99.38% for the positive prediction. The proposed circuit is implemented in 0.18 µm CMOS technology with a 1.8 V supply voltage. Using the proposed circuit, no analog-to-digital converter is required to be used which save a considerable portion of the power and the area. Consuming a 71 nW power, the proposed circuit is suitable for wearable and implantable ECG monitoring applications.