Low-Noise Low-Pass Filter for ECG Portable Detection Systems with Digitally Programmable Range

This paper presents the design of an operational transconductance amplifier-C (OTA-C) low-pass filter for a portable Electrocardiogram (ECG) detection system. A fifth-order Butterworth filter using ladder topology is utilized to reduce the effect of component tolerance and to provide a maximally flat response. The proposed filter is based on a novel class AB digitally programmable fully differential OTA circuit. Based on this, PSPICE simulation results for the filter using 0.25-μm technology and operating under ±0.8 V voltage supply are also given. The filter provides a third harmonic distortion (HD3) of 53.5 dB for 100 mV p-p @50 Hz sinusoidal input, input referred noise spectral density of , total power consumption of 30 μW, and a bandwidth of 243 Hz. These results demonstrate the ability of the filter to be used for ECG signal filtering that is located within 150 Hz.