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Proceedings Paper

A 0.9-V pulse frequency modulation photosensor based on capacitive feedback reset
Author(s): Koutaro Yasuoka; Keiichiro Kagawa; Jun Ohta; Masahiro Nunoshita
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Paper Abstract

We are developing a retinal prosthesis vision chip based on a pulse-frequency-modulation (PFM) photosensor. Because the device is implanted in the eye ball and is powered by RF coil coupling with limited energy, low voltage and small current operation is required to achieve low power dissipation. We propose a capacitive-feedback-reset method for the PFM vision chip. The proposed method uses capacitive feed back through the junction capacitance of the photodiode and gate-source overlap capacitance of the reset transistor. In the proposed PFM circuit, the feed-through effect in resetting contributes to avoid current competition, so that the high dynamic range can be achieved even at the low voltage operation. We have fabricated a pixel TEG circuit in a 0.35-μm CMOS technology. The PFM photosensor circuit is composed of a four-stage inverter-chain. Dynamic range of 136dB has been achieved with 0.8-V power supply.

Paper Details

Date Published: 7 March 2005
PDF: 8 pages
Proc. SPIE 5677, Sensors and Camera Systems for Scientific and Industrial Applications VI, (7 March 2005); doi: 10.1117/12.588226
Show Author Affiliations
Koutaro Yasuoka, Nara Institute of Science and Technology (Japan)
Keiichiro Kagawa, Nara Institute of Science and Technology (Japan)
Jun Ohta, Nara Institute of Science and Technology (Japan)
Masahiro Nunoshita, Nara Institute of Science and Technology (Japan)


Published in SPIE Proceedings Vol. 5677:
Sensors and Camera Systems for Scientific and Industrial Applications VI
Morley M. Blouke, Editor(s)

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