EEG Acquisition And Conversion Circuit Based On Continuous Delta-Sigma Modulator

In recent years,with the penetration and popularization of increasingly intelligent and lightweight electronic devices in the field of modern medicine,the bioelectrical signal monitoring system is gradually developing towards the wearable direction of ultra-low power consumption and high comfort.As a typical bioelectrical signal,cerebral cortex signals are characterized by low frequency and small amplitude.Therefore,EEG acquisition and conversion circuit,as a core part of EEG detection system,needs to have band-pass frequency characteristics and certain anti-interference ability to accurately process signals.In this paper,based on the characteristics of EEG signal and considering the interference and non-ideal factors in practical application scenarios,an EEG acquisition and conversion circuit using continuous delta-sigma modulator is proposed,which is mainly composed of a chopper amplifier and a delta-sigma modulator.It is mainly composed of instrument amplifier and delta-sigma modulator.The capacitive coupled instrument amplifier based on chopper technology realizes high pass Angle frequency through DC servo loop,impedance lifting loop to improve input impedance,and uses MOS pseudo-resistance technology to reduce system area.The delta-sigma modulator uses a feedforward single-loop third-order 1-bit quantization structure.The first-order RC integrator based on a single-stage class-AB amplifier achieves a stable integration coefficient under low power consumption to ensure the resolution of the modulator.The second and third-order integrators adopt an ultra-low power Gm-C integrator to ensure the low power design goal of the modulator.Meanwhile,the Gm circuit with the negative feedback structure of the source pole improves its linearity within the signal range.To ensure the stability of the integration coefficient of Gm-C integrator,so as to ensure the realization of low power consumption and highresolution delta-sigma modulator.In this paper,the EEG acquisition and conversion circuit is designed by Taiwan Semiconductor Manufacturing（TSMC）65nm CMSO technology.At 1.8V power supply voltage,the total power consumption of the circuit is about 4.5μW.According to the simulation results,the gain of the whole circuit is about 39.8d B in the frequency range of 0.5Hz ～ 1k H signal,the equivalent reference noise to the input is about 53nV/Hz^1/2@10Hz,and the circuit can suppress the 50 m V DC offset voltage caused by the electrode,and the input impedance is about 385MΩ@200Hz.The digital output signal with a peak-to-peak value of 5m V is 61.4d B（0～250Hz bandwidth）after the whole acquisition and conversion circuit,and the significant digit is 10.