0.5 V Fifth-Order Butterworth Low-Pass Filter Using Multiple-Input OTA for ECG Applications.

Montree Kumngern,Tomasz Kulej,Nattharinee Aupithak,Fabian Khateb

doi:10.3390/s20247343

Abstract

This paper presents a 0.5 V fifth-order Butterworth low-pass filter based on multiple-input operational transconductance amplifiers (OTA). The filter is designed for electrocardiogram (ECG) acquisition systems and operates in the subthreshold region with nano-watt power consumption. The used multiple-input technique simplifies the overall structure of the OTA and reduces the number of active elements needed to realize the filter. The filter was designed and simulated in the Cadence environment using a 0.18 µm Complementary Metal Oxide Semiconductor (CMOS) process from Taiwan Semiconductor Manufacturing Company (TSMC). Simulation results show that the filter has a bandwidth of 250 Hz, a power consumption of 34.65 nW, a dynamic range of 63.24 dB, attaining a figure-of-merit of 0.0191 pJ. The corner (process, voltage, temperature: PVT) and Monte Carlo (MC) analyses are included to prove the robustness of the filter.

Highlights

Continuous-time filters are widely used in biomedical systems devoted to applications in electroencephalographic (EEG), electromyographic (EMG), and electrocardiographic (ECG) systems.The biological signals processed in these systems typically occupy the frequency range of 0.05–250 Hz, with an amplitude of 15 μV–5 mV [1]
The filtered analog signal is converted into digital form by an analog-to-digital converter (ADC) and it is further processed by a digital signal processing (DSP) block
The paper is organized as follows: Section 2 shows the principle of multiple-input gate-driven operational transconductance amplifiers (OTA) and the filter design based on it, Section 3 the simulation results, and Section 4 the conclusion

Summary

Introduction

Continuous-time filters are widely used in biomedical systems devoted to applications in electroencephalographic (EEG), electromyographic (EMG), and electrocardiographic (ECG) systems. The fifth-order Butterworth low-pass filter using fully differential operational transconductance amplifiers (FD-OTAs) is shown in Figure 3a [7]. This paper proposes a fifth-order Butterworth low-pass filter based on multiple-input operational transconductance amplifiers. It is clearly shown that the number of active devices needed to realize the fifth-order low-pass filter can be reduced by using the multiple-input OTA and results in reducing the power consumption and the active chip area. The paper is organized as follows: Section 2 shows the principle of multiple-input gate-driven OTA and the filter design based on it, Section 3 the simulation results, and Section 4 the conclusion. (c) FDDA-based filter [10]

Multiple-Input Gate-Driven OTA

Proposed Filter

Results and Discussion

Conclusions