Abstract-The neural stimulators have been employed to the visual prostheses system based on the functional electrical stimulation (FES). Due to the size limitation of the implantable device, the smaller area of the unit current driver pixel is highly desired for higher resolution current stimulation system. This paper presents a 16-channel compact current-mode neural stimulator IC with digital to analog converter (DAC) sharing scheme for artificial retinal prostheses. The individual pixel circuits in the stimulator IC share a single 6 bit DAC using the sample-and-hold scheme. The DAC sharing scheme enables the simultaneous stimulation on multiple active pixels with a single DAC while maintaining small size and low power. The layout size of the stimulator circuit with the DAC sharing scheme is reduced to be 51.98 %, compared to the conventional scheme. The stimulator IC is designed using standard 0.18 μm 1P6M process. The chip size except the I/O cells is 437 μm ´ 501 μm.
This paper presents an analog front-end (AFE) IC for measuring biopotential signals such as electroencephalogram (EEG) and, electrocardiogram (ECG). The AFE employs the capacitively coupled chopper instrumentation amplifier architecture to achieve low noise. To reduce chopper ripple and respiration artifacts, a continuous-time AC-coupled ripple reduction loop (RRL) and DC servo loop (DSL) are employed. The proposed IC features differential gain of 72dB, and a common mode rejection ratio (CMRR) of 226 dB at 50 Hz, respectively. The input referred noise is simulated to be 1.6 V rms in the bandwidth from 1 Hz to 100 Hz.
IndexTerms-biomedical circuits, analog IC, electrocardiogram (ECG), electroencephalograph (EEG), instrumentation amplifier (IA).
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