A Novel Differential Log-Companding Amplifier for Biosignal Sensing

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 166.1 fa / hz. this new method is suitable for biomedical applications such as electrocardiogram (ecg) signal acquisition. © 2016 zigang dong et al.