An Analog Front-end Circuit For Biopotential Signal Detection System

In the last few years,there has been a growing interest in the design of wireless sensing device for portable,wearable or implantable biomedical applications.BODY SENSOR NODES?BSNs?are generally used for detecting and monitoring biopotential signalssuchaselectrocardiogram?ECG?,electroencephalogram?EEG?,and electromyogram?EMG?,to name a few.Most biopotential signals are often very slow and exhibit limited dynamic range.BSNs promise to provide significant benefits to the health care domain by enabling continuous monitoring,actuation,and logging of patient bio-signal data,which can help medical personnel to diagnose,prevent,and respond to various illnesses such as diabetes,asthma,and heart attacks.A typical biomedical sensor system consists of a band-pass filter,a low-noise amplifier and an analog-to-digital converter?ADC?.The digitalization of the sensed biopotential signals is usually performed by ADCs with moderate resolution?8–12 bits?and sampling rate?1–1000kS/s?.In such system,energy efficiency and long battery life are paramount design goals.Particularly,analog front-end circuits defines the quality of the extracted signals.Based on the comprehensive consideration of system performance,power and area,this thesis designs an analog front-end circuit composed of a bandpass low-noise amplifier?BP-LNA?with filtering and amplification function and a SAR ADC with prediction function.The gain and bandwidth of the entire front-end amplifier can be adjusted from outside the chip to meet the applications of amplification and filtering of different biopotential signals.In the low noise amplifier,the MOS pseudo resistor technology is proposed to achieve very low high pass corner frequency.The structure achieves low noise low power design requirements combined Careful design of the critical transistors and optimization of the transistor size which eliminates the use of chopping circuits.In the design of SAR ADC,a quantization interval prediction technology for biopotential signal detection is presented in this thesis,which can reduce the average quantization power consumption of low frequency parts of the input signals,and achieve low power consumption design.The chip was fabricated in 130nm CMOS 1P7M standard process,the power supply voltage is 1.2V.The Spectre/Hspice simulation results show that the high pass frequency of analog-front amplifier can be adjustable continuously from 0.28Hz to858.68Hz and the low pass frequency is fixed at 70kHz.The mid band gain is 39.72dB or 45.71dB and the amplifier exhibits 4.6?V_rmsms input referred noise.The SAR ADC achieves a SFDR of 84.0298 dB,a SNDR of 72.4111 dB,and an ENOB of 11.7361 bits under the sampling frequency of 10 kS/s.The total power consumption is 26.92?W,the whole system achieves a SFDR of 79.5349dB,a SNDR of 69.5825dB,an ENOB of11.2662bit,and occupies below 1mm².