Research And Design Of Human Bioelectric Signal Amplifiers

The human body has bioelectrical phenomena that are closely related to life activities in both static and active states.Among various human bioelectrical signals,electrocardiographic signals and neural signals are representative.The ECG signals can be collected directly on the body surface and can be used to diagnose a variety of heart diseases and monitor patient's life signs;the neural signals need to be implanted in the electrodes to detect nerve abnormalities and injuries.The ECG signals and the neural signals have the commonality of human bioelectricity,that is,low frequency,low amplitude,and easy to be covered,so they must be linearly amplified during the acquisition process.At the same time,they are different in characteristics and forms of existence.Therefore,based on the SMIC 0.18?m CMOS process,an ECG signal amplifier for body surface acquisition and a neural signal amplifier for implantable devices are designed to study two different human bioelectric signal amplifiers.In the design of ECG signal amplifier,we need to consider the problem of electrode offset voltage and common mode signal interference during the process of human ECG signal acquisition,and traditional ECG signal amplifiers have some problems such as small input common mode voltage range,high power consumption and large chip area.In this paper,a current feedback amplifier with wide input common mode voltage range and high common mode rejection ratio is used as the main amplifier of ECG signal amplifier.The offset voltage suppression loop is added to reduce the electrode offset voltage by means of negative feedback to ensure that the circuit is biased at the correct static operating point.The right leg drive circuit is integrated to increase the common mode rejection ratio of the system and reduce the effects of common mode interference.The simulation results show that the power consumption is 46.8?W and the common mode rejection ratio is up to 107.4d B at 1.8V supply voltage,which can suppress the electrode offset voltage of±200m V.Its input common mode voltage range is 0?1.55V,and the circuit layout area is 422×315?m~2.In the design of neural signal amplifier,it focuses on ultra-low power design,low noise design and small area design for implantable circuits.The design uses a capacitively coupled chopper amplifier as the main amplifier,which uses chopping technology to reduce the low frequency noise in the circuit,and uses the relaxation oscillator to provide the switching control voltage of the chopper.Finally,a transconductance capacitor low-pass filter is connected to the output of the amplifier to filter out high-frequency interference such as glitch.The simulation results show that the power consumption is only 6.67?W,the common mode rejection ratio is 99.1d B,the input reference noise is 0.79?Vrms at a low supply voltage of 1V,and the circuit layout area is 292×230?m~2.In this paper,an ECG signal amplifier and a neural signal amplifier are designed as representatives to study the human bioelectric signal amplifier.The design results meet the expected requirements and have a certain reference significance for the research of human bioelectric signal amplifier.