DESIGN OF LOW POWER AND LOW OVERHEAD ECG SENSOR FOR BIOMEDICAL APPLICATIONS

Abstract

With the advancement in integrated low power design, there is growing trend in biomedical engineering which combines medical sciences with latest innovations to produce medical devices and sensors which monitors and diagnosis various diseases. The primary block in heart monitoring systems is the design of low power and low noise analog front-end circuit for Electrocardiogram (ECG) acquisition. In ECG signal, QRS complex are of higher magnitude and frequency compared to P and T wave. Considering this characteristic, a low power and low overhead ECG sensor which detects QRS complex of the ECG signal is designed. This topology replaces conventional ECG monitoring system which consumes more power. The ECG signal amplitude varies from mV to μV depending on the area where the electrodes are placed. A Programmable gain amplifier (PGA) is designed which accepts ECG signal and then amplifies with corresponding gain and thus removes both electrode skin interface DC offset voltage and out of band noise. The amplified signal is then passed through QRS and baseline amplifier which preserves QRS complex and motion artifacts respectively. Further, the signal is applied to VDC generator which adds some considerable DC voltage to the amplified ECG signal. The comparator outputs a digital pulse whenever a QRS complex is detected by taking inputs from VDC generator. Additionally, a current reference circuit is designed which biases all the amplifiers. RR Interval of ECG signal is also calculated by averaging the time period between two consecutive digital pulse of comparator output.