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Journal of Sensors
Volume 2016, Article ID 5358963, 7 pages
Research Article

A Novel Differential Log-Companding Amplifier for Biosignal Sensing

1Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, 1068 Xueyuan Road, Xili, Nanshan, Shenzhen, Guangdong 518055, China
2Key Laboratory for Health Informatics of the Chinese Academy of Sciences (HICAS), 1068 Xueyuan Road, Xili, Nanshan, Shenzhen, Guangdong 518055, China
3Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, Hong Kong

Received 23 May 2016; Accepted 31 July 2016

Academic Editor: Stephane Evoy

Copyright © 2016 Zigang Dong et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We proposed a new method for designing the CMOS differential log-companding amplifier which achieves significant improvements in linearity, common-mode rejection ratio (CMRR), and output range. With the new nonlinear function used in the log-companding technology, this proposed amplifier has a very small total harmonic distortion (THD) and simultaneously a wide output current range. Furthermore, a differential structure with conventionally symmetrical configuration has been adopted in this novel method in order to obtain a high CMRR. Because all transistors in this amplifier operate in the weak inversion, the supply voltage and the total power consumption are significantly reduced. The novel log-companding amplifier was designed using a 0.18 μm CMOS technology. Improvements in THD, output current range, noise, and CMRR are verified using simulation data. The proposed amplifier operates from a 0.8 V supply voltage, shows a 6.3 μA maximum output current range, and has a 6 μW power consumption. The THD is less than 0.03%, the CMRR of this circuit is 74 dB, and the input referred current noise density is . This new method is suitable for biomedical applications such as electrocardiogram (ECG) signal acquisition.