A Low-noise Low-power Chopper Amplifier For Neural Signal Detection Front-end

The detection of neural signals plays a vital role in the research of neuroscience,the treatment of neurological diseases and the development of new applications such as brain-computer interfaces.The use of integrated circuit technology to record and process the electrical characteristics of neural signals has become a hot research issues in both academic and industrial fields.A low noise amplifier(LNA)plays an important role in the circuit front-end for neural signal detection.The low-frequency and low-amplitude characteristics of neural signals poses challenges to neural signals recording.At the same time,there are many kinds of interference signals in the detection process,and it is necessary to have a certain understanding of the characteristics of the electrodes.In order to avoid the interference of low frequency flicker noise that is common in integrated circuit,a chopper-stabilized analog front-end amplifier(FEA)for neural signal acquisition is presented in this paper.It uses chopper amplifier structure to carry out frequency modulation to solve the interference of low-frequency flicker noise and offset in the circuit,while adopting a new circuit structure to solve the noise and offset interference caused by the servo loop in the chopper amplifier structure.The proposed FEA employs a switched-capacitor(SC)integrator with offset and low-frequency noise compensation.Moreover,a dc-blocking impedance is placed for ripple-rejection(RR),and a positive feedback loop is employed to increase input impedance.The proposed circuit is design in a 0.18-?m 1.8-V CMOS process,completed the schematic design and layout design and post-simulation work under a variety of working environments.It achieves a bandwidth of up to 9 k Hz for local field potential and action potential signals acquisition.The referred-to-input(RTI)noise is 0.72?V_rms in the 1?200Hz frequency band and 3.46?V_rms in the 200?5k Hz frequency band.The noise effect factor is0.43(1?200 Hz)and 2.08(200?5k Hz).Common-mode rejection ratio(CMRR)higher than87d B and power-supply rejection ratio(PSRR)higher than 85d B are achieved in the entire pass-band.It consumes a power of 3.96?W/channel and occupies an area of 0.244 mm²/channel.