MOSFET Integration Capacitor Image Sensor Dynamic Range
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Solution Overview
Problem
Image sensing devices face challenges in achieving high dynamic range capabilities and low kTC reset noise, particularly in varying ambient light conditions, due to the dichotomy between small integration capacitors for low light and large capacitors for high light situations, and the inherent inefficiencies in reset noise associated with typical unit cells.
Innovation Solution
Incorporating a MOSFET with a small integration capacitor and a control mechanism to modulate total capacitance, allowing for dual gain settings and minimizing reset noise by selectively engaging the MOSFET's capacitance in conjunction with the integration capacitor, thereby optimizing performance in both low and high ambient light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a typical unit cell configuration is used, then device complexity is minimized, but kTC reset noise increases
Solution Approach 1:
The patent segments the capacitance function between two distinct components: the integration capacitor and the MOSFET. This segmentation allows independent optimization - the integration capacitor can be small while the MOSFET provides additional capacitance when needed, reducing kTC reset noise without requiring a large fixed integration capacitor, thus resolving the contradiction between simplicity and noise reduction.
Solution Approach 2:
The MOSFET serves multiple functions: it acts as a switch for controlling capacitance coupling and simultaneously provides additional capacitance to reduce kTC reset noise. This multi-functionality allows the unit cell to achieve low noise performance without proportionally increasing complexity, resolving the contradiction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides improved image sensing with high dynamic range and lower kTC reset noise, enhancing signal-to-noise ratio and injection efficiency, while minimizing the limitations of traditional unit cells in both low and high light environments.
Implementation Method 1
The MOSFET is operable to store a first portion of an electric charge corresponding to a detected light intensity
Implementation Method 2
The integration capacitor is operable to store a second portion of the electric charge corresponding to the detected light intensity
Implementation Method 3
Image sensing circuits typically consist of an array of detectors and unit cells that generate and store a charge in proportion to the light intensity received at the location of each detector
Data Source
AI summary
A unit cell includes a MOSFET and an integration capacitor. The MOSFET includes a source, a drain, and a gate. The drain is coupled to the source, and the MOSFET is operable to store a first portion of an electric charge corresponding to a detected light intensity. The integration capacitor includes a first end and a second end. The first end is coupled to the drain of the MOSFET and the second end is coupled to a ground. The integration capacitor is operable to store a second portion of the electric charge corresponding to the detected light intensity.