Digitally programmable OTA-C low pass filter for ECG detection systems

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 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 0:25μm technology and operating under ±0:8V voltage supply are also given. The filter provides a third harmonic distortion (HD3) of 53.5dB for 100mV_p-p sinusiodal input, input referred noise spectral density of 50μV_rms/√Hz, total power consumption of 26μW and a bandwidth of 243Hz. These results demonstrate the ability of the filter to be used for ECG signal filtering which is located within 150Hz.