Comparator Circuit Layout for Smaller Band-Limiting Capacitors
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Solution Overview
Problem
Existing imaging devices face a challenge in reducing noise generated at the time of inversion of a comparator circuit while maintaining the size of the band limiting capacitor.
Innovation Solution
The imaging device incorporates a comparator circuit with a band limiting capacitor connected between the output unit of a first amplifier circuit and the input unit of a second amplifier circuit, and a resistance element connected to the power supply potential, allowing the capacitor's other end to be connected to a node formed between these units, thereby reducing the size of the band limiting capacitor while maintaining the slew rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the capacitance of the band limiting capacitor is increased to enhance noise reduction effect, then the noise reduction performance is improved, but the device area increases
Solution Approach 1:
A resistance element is introduced as an intermediary component between the band limiting capacitor and the power supply potential. This resistance element enables the capacitor to achieve effective noise reduction with reduced capacitance value, thereby reducing the capacitor area while maintaining noise reduction performance
Solution Approach 2:
The invention changes the electrical parameters of the comparator circuit by introducing a resistance element that modifies the time constant and frequency response characteristics. This allows the band limiting capacitor to operate effectively with smaller capacitance, resolving the contradiction between noise reduction and capacitor size
2Speed
If the capacitance of the band limiting capacitor is increased to increase slew rate, then the slew rate is improved, but the device area increases
Solution Approach 1:
The resistance element serves as a mediator that works in conjunction with the band limiting capacitor to achieve the desired slew rate. By controlling the RC time constant, the resistance element enables adequate charging/discharging rates without requiring large capacitor values, thus maintaining high slew rate with reduced capacitor area
Data Source
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AI summary
Provided is an imaging device capable of reducing a size of a band limiting capacitor while reducing noise generated at the time of inversion of a comparator circuit. An imaging device of the present disclosure is an imaging device including an A/D converter including a comparator circuit, in which the comparator circuit includes a first amplifier circuit, a second amplifier circuit provided at a subsequent stage of the first amplifier circuit, a band limiting capacitor provided between an output unit of the first amplifier circuit and an input unit of the second amplifier circuit, and a resistance element with one end directly or indirectly connected to power supply potential or reference potential, and one end of the band limiting capacitor is connected to a first node formed between the output unit of the first amplifier circuit and the input unit of the second amplifier circuit, and another end of the band limiting capacitor is connected to a second node formed in a middle or a terminal of the resistance element.