Signal processing device, including charge injection circuit, and photodetection device
First Claim
1. A signal processing device that outputs an electrical signal having a value according to an amount of charge generated in a photodiode according to an amount of incident light onto the photodiode, comprising:
- an integration circuit including an integration capacitor element that accumulates a charge output from the photodiode, for outputting a voltage value according to an amount of the charge accumulated in the integrating capacitor element;
a comparator circuit for comparing the voltage value output from the integration circuit and input thereto with a predetermined reference value, and when the voltage value has reached the reference value, outputting a saturation signal indicating that fact;
a charge injection circuit for, based on the saturation signal output from the comparator circuit, injecting a constant amount of charge having a polarity opposite to that of the charge accumulated in the integrating capacitor element of the integration circuit into the integrating capacitor element;
a counter circuit for, based on the saturation signal output from the comparator circuit, counting a number of times that the voltage value output from the integration circuit has reached the reference value;
a holding circuit for holding and outputting the voltage value output from the integration circuit;
an amplifier circuit for outputting a voltage value that is K times as large as the voltage value held and output by the holding circuit and input thereto (where K>
1);
an A/D converter circuit in which a voltage value that is K times as large as the reference value is set as a maximum input voltage value, for outputting a digital value corresponding to the voltage value output from the amplifier circuit and input thereto; and
further comprising a reference value generating circuit for being input with a reference value to set the maximum input voltage value in the A/D converter circuit, and supplying a voltage value one K-th as large as this reference value to the comparator circuit as the reference value.
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Accused Products
Abstract
In a signal processing device of an embodiment, an integration circuit accumulates a charge from a photodiode in an integrating capacitor element, and outputs a voltage value according to the amount of charge. A comparator circuit, when the voltage value from the integration circuit has reached a reference value, outputs a saturation signal. A charge injection circuit, in response to the saturation signal, injects an opposite polarity of charge into the integrating capacitor element. A counter circuit performs counting based on the saturation signal. A holding circuit holds the voltage value from the integration circuit. An amplifier circuit outputs a voltage value that is K times (where K>1) larger than the voltage value held by the holding circuit. An A/D converter circuit sets a voltage value that is K times larger than the reference value as the maximum input voltage value, that is, a full-scale value, and outputs a digital value corresponding to the voltage value from the amplifier circuit.
9 Citations
5 Claims
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1. A signal processing device that outputs an electrical signal having a value according to an amount of charge generated in a photodiode according to an amount of incident light onto the photodiode, comprising:
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an integration circuit including an integration capacitor element that accumulates a charge output from the photodiode, for outputting a voltage value according to an amount of the charge accumulated in the integrating capacitor element; a comparator circuit for comparing the voltage value output from the integration circuit and input thereto with a predetermined reference value, and when the voltage value has reached the reference value, outputting a saturation signal indicating that fact; a charge injection circuit for, based on the saturation signal output from the comparator circuit, injecting a constant amount of charge having a polarity opposite to that of the charge accumulated in the integrating capacitor element of the integration circuit into the integrating capacitor element; a counter circuit for, based on the saturation signal output from the comparator circuit, counting a number of times that the voltage value output from the integration circuit has reached the reference value; a holding circuit for holding and outputting the voltage value output from the integration circuit; an amplifier circuit for outputting a voltage value that is K times as large as the voltage value held and output by the holding circuit and input thereto (where K>
1);an A/D converter circuit in which a voltage value that is K times as large as the reference value is set as a maximum input voltage value, for outputting a digital value corresponding to the voltage value output from the amplifier circuit and input thereto; and further comprising a reference value generating circuit for being input with a reference value to set the maximum input voltage value in the A/D converter circuit, and supplying a voltage value one K-th as large as this reference value to the comparator circuit as the reference value. - View Dependent Claims (2, 3, 4, 5)
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Specification