Browsing by Author "Yang, Wen-Chia"

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A CMOS Bio-Inspired 2-D Motion Direction Sensor Based on a Direction Computation Method Derived From the Directionally Selective Ganglion Cells in the Retina
(2011-12-01)
Yang, Wen-Chia
;
Lin, Li-Ju
;
Chiueh, Herming
;
Wu, Chung-Yu
;
電子工程學系及電子研究所
A CMOS bio-inspired motion direction sensor structure and its associated computation method are proposed. Both method and structure with excitation-inhibition operation are derived from the directionally selective ganglion cells (DSGCs) in the retina to mimic their functions. Edge-number normalization for direction calculation and pseudo-random tessellation (PRT) structure for pixel layout arrangement are also proposed to enhance the accuracy of the computation. An experimental chip based on the proposed method and structure has been designed, fabricated, and measured. The chip comprised 32 x 32 pixels with a pixel size of 63 x 63 mu m(2) and a fill factor of 12.8%. The total chip size is 3.3 x 4.2 mm(2) and the power consumption is 9.9 mW in the dark and 21 mW at a maximum clock rate of 10 MHz with 3.3-V power supply. The fabricated chip has been measured with different moving patterns, and a computation error of less than 11 degrees has been accomplished. This verifies the correct functions of the proposed motion direction sensor. With the capability of real-time motion detection and processing under low power dissipation, the proposed sensor is feasible for many applications.
Responses of Rabbit Retinal Ganglion Cells to Subretinal Electrical Stimulation Using a Silicon-Based Microphotodiode Array
(2011-12-01)
Yang, Ya-Ting
;
Lin, Po-Kang
;
Wan, Chen
;
Yang, Wen-Chia
;
Lin, Li-Ju
PURPOSE. With subretinal prostheses, retinal ganglion cells (RGCs) are activated by electrical stimulation of the retinal neural network. The aim of this study was to evaluate the efficacy of silicon-based solar cells in evoking RGC responses by electrically stimulating the photoreceptor side of an isolated retina. METHODS. A light-bleached retina of an adult New Zealand White rabbit was placed with its photoreceptor side down onto a silicon chip that consisted of a 4 x 4 microphotodiode array (MPDA). The stimulating current was elicited by activating the solar cell with a 532-nm laser light source. Responses of the ON and OFF alpha RGCs on electrical stimulation were recorded extracellularly. Recorded RGCs were then injected with 4% N-(2-aminoethyl)-biotinamide hydrochloride to allow cell type identification. RESULTS. Using a design that includes a circumvented ground electrode, the authors successfully evoked spiking responses by the ON and OFF alpha RGCs in an isolated rabbit retina using low light power to activate the MPDA (equivalent to 39 mu C/cm(2)). The charge density-dependent response and the frequency-dependent pair-pulse suppression were characterized. The spike latency of the RGC responses triggered by electrical stimulation was equivalent to the latency of its light response, which supports the hypothesis that the activation is mediated by the retinal neural network. CONCLUSIONS. Reliable activation of RGCs by electrical stimulation in vitro using an MPDA demonstrates the feasibility of developing solar cell-based subretinal prostheses that potentially could be developed into a power-free device able to restore vision. (Invest Ophthalmol Vis Sci. 2011; 52: 9353-9361) DOI: 10.1167/iovs.11-7808
The Design of CMOS General-Purpose Analog Front-End Circuit with Tunable Gain and Bandwidth for Biopotential Signal Recording Systems
(2011)
Chen, Wei-Ming
;
Yang, Wen-Chia
;
Tsai, Tzung-Yun
;
Chiueh, Herming
;
Wu, Chung-Yu
In this paper an 8-channel CMOS general-purpose analog front-end (AFE) circuit with tunable gain and bandwidth for biopotential signal recording systems is presented. The proposed AFE consists of eight chopper stabilized pre-amplifiers, an 8-to-1 analog multiplexer, and a programmable gain amplifier. It can be used to sense and amplify different kinds of biopotential signals, such as electrocorticogram (ECoG), electrocardiogram (ECG) and electromyogram (EMG). The AFE chip is designed and fabricated in 0.18-mu m CMOS technology. The measured maximum gain of AFE is 60.8 dB. The low cutoff frequency can achieve as low as 0.8 Hz and high cutoff frequency can be adjusted from 200 Hz to 10 kHz to suit for different kinds of biopotential signals. The measured input-referred noise is 0.9 mu Vr, with the power consumption of 18 mu W per channel at 1.8-V power supply. And the noise efficiency factor (NEF) is only 1.3 for pre-amplifier.