An ultra-low power analog QRS-detection circuit for ambulatory ECG monitoring

In this paper, an ultra-low-power QRS-detection circuit is proposed which is suitable for wearable and implantable ECG-monitoring applications. Implementing the major part of the system in the analog-domain using current-mode circuits in the subthreshold region leads to an extremely low power consumption. The proposed circuit is based on calculating the energy of the derivative of the signal which follows by the onset spike detection method. Two low-pass filters with ultra-low cutoff frequencies of 6.45 Hz and 0.23 Hz are utilized in this method which are required for removing the high-frequency noise and estimating the required threshold for QRS-detection, respectively. The proposed algorithm is evaluated over the entire standard MIT-BIH arrhythmia database which results in a detection error rate of 1.46% with sensitivity and positive prediction of 99.17% and 99.36%, respectively. This QRS-detector circuit is implemented in 0.13 μm CMOS technology with a power supply of 1.2 V which consumes 31.5nW power and occupies 0.097 mm2 of silicon area. As the proposed circuit uses the analog ECG signal, there is no need to use an analog-to-digital converter which yields to further save in the area and power consumption of the entire system.