Research And Design Of Microelectronic EMG Signal Bridge Key Circuit

Treatment and rehabilitation of paralyzed patients is a difficult problem in medicine fields. Rehabilitation effect of the existing biological methods which are low efficient and high cost varies from person to person. With the development of information technology, electrical information science and biology cross, using microelectronics IC to bridge the damaged central nerve offers a new way to restore the function of central nervous system.The related theories of EMG signal bridge is analyzed firstly. Based on the premier experiment of the research group, this paper proposes methods of using concentric electrodes as stimulating electrodes and determines the performance index. The EMG signal bridge key circuit chip is designed in CSMC0.5μm CMOS process. It is composed of an EMG signal detecting circuit, a DC offset compensating circuit, a band-pass filter circuit and a signal amplification circuit. Two specialized operational amplifiers are designed:a two stages folded cascade op-amp and a two stages constant-transconductance rail-to-rail input-output op-amp.As post-simulation shows, the two stages folded cascade op-amp provides 104.6dB gain,86.4°phase margin,7.9MHz bandwidth and 7.75×10-16 V2/Hz@1kHz input noise. The two stages constant-transconductance rail-to-rail input-output op-amp provides almost rail-to-rail input and output voltage and 4.9% error. Both of the two op-amps satisfy the special demands. The filter in the chip adjusts operating frequency by adjusting the cap outside the chip. Die area of the chip is 1150μm×950μm. The system chip’s supply voltage is ±2.5V. The power consumption is 4.57mW. The bandwidth is from 95.98 Hz to 6.26 kHz with 33nF external capacitor. The circuit can bridge and amplify signal in this bandwidth.The lower cut-off frequency of the circuit above is 95.98Hz while EMG signal exists under the frequency. As the bandwidth of the circuit designed did not correspond to the EMG signal bandwidth. The circuit is modified. The new circuit designed with switched capacitor filter circuit reduces its lower cut-off frequency, which can adjust the operating frequency by adjusting the sampling signal frequency so can satisfy animal experiments and clinical trials. The system chip’s supply voltage is ±2.5V. Die area of the chip is 1150μm×1000μm. The bandwidth is from 1.15 Hz to 2.65 kHz. The power consumption is 5.33mW. The improved circuit can amplify the EMG signal and filter the interference signal.