The Design And Study Of CMOS Analog Front-end Chip For Biomedical Electrical Signal

With the semiconductor technology used in the biomedical field, an interdisciplinarysubject called Biomedical Microelectronics is developing rapidly. This technology is orientedto human health, integrates the information technology and life science with the maturetechnology of semiconductor science, and combines with varieties of theories and methods ofmaterials science, chemistry, and physics, so it has a significant scientific value and socialsignificance. Since the Analog Front-End circuit is an important bridge to connect thebiomedical signals and the subsequent signal processing, it plays an important role in thebiomedical signal acquisition system. This paper researched an Analog Front-End chip ofCMOS integrated circuits based on biomedical signal in order to extract biomedical signaleffectively.Through the analysis of biomedical signal characteristic and making board-level systemsof an ECG Analog Front-End circuit, this paper explored, analyzed and validated the designidea of Analog Front-End circuit in chip-level system for biomedical signal. After the analysis,calculation and simulation of the overall system, an Analog Front-End circuit with low noise,low power, variable gain and bandwidth was presented. The Analog Front-End chip wasmostly composed of low-noise preamplifier, variable gain amplifier, switched-capacitor filterand bias circuit. The preamplifier used “T-Type Feedback” AC-coupled structure, with thefeature of low noise and high suppression of baseline drift; Variable gain amplifier canamplify the acquired biomedical signal to the acceptable range of back-end circuit; Four-orderswitch capacitance filter can inhibit the noise out of the bandwidth of the signal, and eliminatealiasing noise produced by the ADC acquisition. The simulation results showed that theproposed preamplifier attained an equivalent input integral noise of3.508μV, a pointfrequency noise in the bandwidth less than300nV, with the power consumption of42.7μW.The gain and bandwidth of the analog front-end circuit can be adjusted, which frequencyspectrum dropped at the speed of95dB every10times frequency at High frequency cutoffpoint, therefore it can restrain the out-of-band noise and improve signal-to-noise ratio of theoutput signal.The proposed IC has been fabricated in UMC0.18-μm CMOS2P6M technology withcore area of785μm485μm. Experiment results indicated that the equivalent input integralnoise of the preamplifier was less than5.33μV and the point frequency noise in the bandwidthwas less than300nV, the low-frequency cutoff and high-frequency cutoff can be adjustedfrom0.1Hz to310Hz and5kHz to10kHz. Power dissipation of each channel was approximately1.47mW under a1.8V single supply voltage. The experimental resultsdemonstrated that this analog front-end IC was appropriate for a wide range of biomedicalapplications.