| Recently implantable and portable biomedical instrumentation has stepped into people’s eyesight. Multi-channel bio-signal acquisition system is one of its core modules. In order to satisfy the design requirements, such as multi-channel, high signal fidelity and low power consumption, this thesis proposed a high-resolution low-power incremental Sigma-Delta ADC for multi-channel bio-signal acquisition systems.The thesis consists of the Sigma-Delta modulator design and digital decimation filter design. Different from the traditional Sigma-Delta ADC, additional reset signal and oversampling rate limitation should be taken into consideration for the design of the incremental Sigma-Delta ADC. After considering the system requirements and comparing the performance of different structure, the proposed modulator in this thesis utilizes the3rd-order1-bit CIFF architecture. In system modeling and simulation, noise and OTAs’non-ideal factors, like DC gain, gain bandwidth (GBW) and slew-rate (SR), are added into the ideal model to mimic the real situations.One stage current-mirror structure is adopted in our proposed work to the OTAs in integrators. Current-starvation technique is aim at improving the DC gain and GBW, and four compensation resistors are used to ensure the stable work. To suppress the flicker noise, chopper stabilization technique is utilized in the modulator. Moreover, the clock signal voltage boosting circuits are used to avoid the nonlinearity caused by the low power supply voltage. The simulation results show that the proposed modulator works well and achieves an SNDR of96.9dB, a power consumption of40μW and a FOM value of435fJ/conversion-step.Besides, the digital decimation filter that consists of a cascaded of integrators comb (CIC) filter and two half-band filters has also been realized. The results show that the filter is able to well realize the functions of down-sampling the filtering, and does not affect the performance of the outputs of the modulator. |
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