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US 5,861,621 AGranted
Photosensor circuit having an initial setting unit
AssigneeHonda Giken Kabushiki Kaisha
InventorsKatsuhiko Takebe, Hiroshi Abe
Life of this patent
Estimating the term…
Abstract
A photosensor circuit comprises a photoelectric transducer, an n-channel MOS transistor and an initial setting unit for precluding the occurrence of a residual image phenomenon. When an optical signal is generated by the photoelectric transducer, the initial setting unit sets the gate voltage of the n-channel MOS transistor at a high value for a predetermined time to lower the drain-source impedance of the n-channel MOS transistor to thereby control charge or discharge of a capacitor connected to a source terminal.
Claims4
A photosensor circuit comprising:
- a photoelectric transducer for detecting an optical signal and providing a sensor current;
- an n-channel MOS transistor connected in series with said photoelectric transducer for converting the sensor current detected by said photoelectric transducer into a detected voltage having a logarithmic characteristic in a weakly inverted state;
- and
- an initial setting unit for, after detection of the optical signal by said photoelectric transducer, setting a gate voltage of said n-channel MOS transistor at a value higher than a predetermined value for a predetermined time to lower an impedance between a drain and a source of said n-channel MOS transistor to thereby control charge or discharge of a capacitor connected to a detection terminal disposed at a junction between said photoelectric transducer and said n-channel MOS transistor.
1 more element
A photosensor circuit comprising:
- a photoelectric transducer for detecting an optical signal and generating a sensor current;
- a p-channel MOS transistor connected in series with said photoelectric transducer for converting the sensor current generated by said photoelectric transducer into a detected voltage having a logarithmic characteristic in a weakly inverted state;
- a switching p-channel MOS transistor connected in parallel with said p-channel MOS transistor;
- and
- an initial setting unit for, after detection of the optical signal by said photoelectric transducer, setting a gate voltage of said switching p-channel MOS transistor at a value lower than a predetermined value for a predetermined time to lower an impedance between a drain and a source of said switching p-channel MOS transistor to thereby control charge or discharge of a capacitor connected to a detection terminal disposed at a junction between said photoelectric transducer and said p-channel MOS transistor.
2 more elements
Dependencies are inferred from the claim text.