Solid-state image sensing device
First Claim
1. A solid-state image sensing device comprising:
- a photodiode for producing a charge in correspondence with an intensity of light thereby, said photodiode having a first terminal set at a first reference voltage level and a second terminal for outputting the produced charge, and the first reference voltage level falling within a range between second and third reference voltage levels;
a first feedback capacitive element having a first terminal which directly receives the charge output from the second terminal of said photodiode;
a first amplifier having a signal input terminal connected to the first terminal of said first feedback capacitive element, the signal input terminal of said first amplifier being virtually set at the first reference voltage level, and an output terminal of said first amplifier being connected to a second terminal of said first feedback capacitive element;
a first step charge generator for producing a step charge on the basis of the second and third reference voltage levels, the first step charge generator supplying the step charge to said first feedback capacitive element;
a voltage comparator for receiving a first integral voltage signal output from said first amplifier, comparing a voltage of the first integral voltage signal with the first reference voltage level, and outputting a comparison result signal;
a binary sampling circuit for receiving the comparison result signal, and sampling the comparison result signal to binarize the comparison result signal; and
a fundamental timing generation circuit for generating a first clock signal and a second clock signal being at logical false level when the first clock signal is at logical truth level and changing to logical truth level during a period included in a logical false level period of the first clock signal, outputting the first and second clock signals to said first step charge generator, and outputting the first clock signal to said binary sampling circuit.
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Accused Products
Abstract
When a photodiode receives light, it produces a charge corresponding to the intensity of light, and outputs it as a current signal. The current signal is input to an integral circuit constituted by a feedback capacitive element and a charge amplifier, and is integrated by time. On the other hand, a step charge generator generates a charge corresponding to one of reference voltage levels +Vref and -Vref in response to first and second clock signals CLK1 and CLK2, and supplies the charge to the feedback capacitive element in synchronism with the clock signal. The integral circuit executes an integral operation by accumulating the charge produced by the photodiode, and supplies a step charge, thus executing ΣΔ modulation. An AD conversion result is obtained from the ΣΔ modulation result. In this manner, high-precision digital data is output in correspondence with the intensity of light by the photodiode with a simple circuit arrangement.
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Citations
15 Claims
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1. A solid-state image sensing device comprising:
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a photodiode for producing a charge in correspondence with an intensity of light thereby, said photodiode having a first terminal set at a first reference voltage level and a second terminal for outputting the produced charge, and the first reference voltage level falling within a range between second and third reference voltage levels; a first feedback capacitive element having a first terminal which directly receives the charge output from the second terminal of said photodiode; a first amplifier having a signal input terminal connected to the first terminal of said first feedback capacitive element, the signal input terminal of said first amplifier being virtually set at the first reference voltage level, and an output terminal of said first amplifier being connected to a second terminal of said first feedback capacitive element; a first step charge generator for producing a step charge on the basis of the second and third reference voltage levels, the first step charge generator supplying the step charge to said first feedback capacitive element; a voltage comparator for receiving a first integral voltage signal output from said first amplifier, comparing a voltage of the first integral voltage signal with the first reference voltage level, and outputting a comparison result signal; a binary sampling circuit for receiving the comparison result signal, and sampling the comparison result signal to binarize the comparison result signal; and a fundamental timing generation circuit for generating a first clock signal and a second clock signal being at logical false level when the first clock signal is at logical truth level and changing to logical truth level during a period included in a logical false level period of the first clock signal, outputting the first and second clock signals to said first step charge generator, and outputting the first clock signal to said binary sampling circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification