| Summary: | 碩士 === 國立中央大學 === 電機工程研究所 === 98 === With the rapid development of medical science and very large scale integration circuit, medical electronic devices which are used to implant in the human body have been evolved. Furthermore, some medical electronic devices have already been applied for regulating human’s physiological functions, stimulating nerves, muscles, and treatment of many diseases. This thesis aims to design an electrical stimulator for implanted visual prosthesis. The designed electrical stimulator stimulates nerves or muscles using electrodes as the interface. In general, the electrode-tissue interface impedance may changes in the rage of 10–100 KΩ due to poor contact, the electrode size and material differences, or electrode-self by stimulus current and environmental factors, and so on. Using impedance measurement circuit to measure interface impedance before stimulated, and this thesis proposes the digital pulse width modulator to produce proper pulse widths for different interface impedances, enabling electrical stimulator to adjust the stimulus charge, thus making electrical stimulator to achieve the best effect.
However, the stimulus current is limited by the supply voltage, effective stimulating may be unable to be achieved in a stimulus period when the interface impedance is too large. In order for electrical stimulator to satisfy the requirement of impedance variation, this thesis also proposes a high voltage output driver, which can generate three times supply voltage output, for the voltage-controlled electrical stimulator. Moreover, such a high voltage output driver accommodating to impedance variation and stimulus parameter setting is implemented in TSMC 0.18μm standard CMOS technology to demonstrate the feasibility of the proposed electrical stimulator. An advantage of the designed high voltage output driver is that it can be fully integrated within other circuit without extra process costs.
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