Design And Implementation Of Front-End Amplifier Chip For Bio-Electrical Signal Acquisition System

Bio-electrical signal is a natural electrical signal generated by complex organism.It reflects vital signs,status and other information of living beings.With the increasing development of integrated circuits as well as the huge demand of daily healthcare,brain-machine interface and etc.,wearable bio-electrical signal acquisition systems have attracted a lot of attention.In portable devices,low noise and low power consumption front-end amplifier is one of the most critical block because it connects the electrodes directly and determines the signal quality from the source.This thesis mainly aims to design and implement front-end amplifier and analyze the problems of this structure deeply.First of all,bio-electrical signal acquisition is introduced briefly.Then,analysis and conclusion of the advanced acquisition integrated circuits are given from the view of development trend.Low noise and low power consumption are two critical parts to be considered.AC coupling which can reject DC offset and has high input impedance is adopted.Considering the tradeoff among low noise,low power consumption and other performance,a telescopic structure with all the transistors working in sub-threshold region is chosen in the fully differential OTA design.Moreover,the sizing method based on g_m/I_D methodology,as well as the impedance boosting technique,pseudo resistor module and quasi-floating gate technique is discussed.For better signal quality,several design methods are introduced to minimize mismatch and shielding specific component from substrate noise in the layout design.The reasons of CMRR's large degradation are analyzed thoroughly with theoretical derivation and simulation verification.And the methods to solve this problems are also presented finally.The chip is fabricated under XFAB 0.35?m 2P4M CMOS process.The supply voltage is set to 3V.Post layout simulation shows of the front-end amplifier achieved power consumption of 2.7?W for every channel,integrated equivalent input-referred noise of 1.78?Vrms over the0.5Hz-200Hz frequency range,closed loop gain of 41dB,high pass cutoff frequency of 0.5Hz and low pass cutoff frequency of 400Hz.The noise efficiency factor is 3.4,close to the advanced level,compared with recent leading publications.