A Novel Differential Log-Companding Amplifier for Biosignal Sensing

Abstract EN

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.