Research And Design Of Low Power Bio-Signal Acquisition Analog Front-End

With the development of microelectronics and the Internet of Things technology in recent years,wearable medical devices have increasingly appeared in people's daily lives.Wearable medical devices can allow people to view their physiological indicators in real time,know their health status,and have a very positive effect on the prevention and treat-ment of some chronic diseases.In wearable medical equipment,the analog front-end is responsible for the acquisition and amplification of bio-signals,and its performance often determines the signal quality that the entire system can get.Bio-signals usually have low frequency and low amplitude.When acquire bio-signals,due to the existence of large-scale common-mode interference in the environment,electrode offset and electrode mismatch,etc.,have brought difficulties to the acquisition of bio-signals,and also have very high requirements for the performance of the analog front-end.For the analog front-end of biological signal acquisition,high common-mode rejection ratio,low noise and offset,high input impedance,and low power consumption are the required performance characteristics.Based on the research of the instrumentation amplifier of the analog front-end,this paper introduces two high-performance instrumentation amplifiers with different structures,and gives their design considerations and verification results.The first is a capacitively coupled chopper instrumentation amplifier.It uses chop-ping modulation technology to reduce amplifier flicker noise and improve common-mode rejection ratio.It uses a ripple suppression technology to eliminate the output ripple in-troduced by chopping,and improves the input impedance of the instrumentation amplifier by introducing a positive feedback loop.A new pseudo-resistor structure is proposed to solve the problem of current leakage in pseudo-resistors.The design is completed under the 180 nm CMOS process and taped out.Test results show that it has an adjustable gain of 6～24 dB,a common-mode rejection ratio of more than 90 dB,and consumes 480 nA of current from a 1.8 V supply.Then there is an AC-coupled current feedback instrumentation amplifier.It uses a current feedback structure and uses capacitors as a voltage divider to achieve high common-mode rejection ratio and low power consumption.In order to suppress the influence of electrode offset,it uses a special input filter circuit,which can achieve AC coupling of signals without reducing the common-mode rejection ratio.There is also a DC feedback loop inside the amplifier to reduce the offset voltage of the amplifier itself.This design is designed and simulated in a 180 nm CMOS process.It has a gain of 40 dB,a common-mode rejection ratio of 136 dB,and 5.87μV_rms（0.5Hz～10kHz）input reference noise,5.5μV input offset voltage and NEF of 2.75,and the power supply voltage is 1.8 V,the total current consumption is 1.48μA.