Column Comparator Circuit Using Digital Transistors for Fast Image Sensing
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Solution Overview
Problem
Conventional image sensor circuits rely on numerous analog comparators, leading to significant power consumption and vertical fixed-pattern noise, with slow conversion speeds due to the use of analog transistors, which are inefficient and limit the performance of digital signal conversion.
Innovation Solution
The implementation of a comparator system that includes digital transistors and a charge sharing circuit to reduce the signal range of input signals, allowing for efficient comparison and conversion of light signals to digital format, utilizing a charge sharing circuit with capacitors and amplifiers to manage signal levels and improve conversion speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional analog comparators are used for signal conversion, then the circuit can process analog signals directly, but power consumption increases and conversion speed decreases
Solution Approach 1:
The patent replaces analog transistors with digital transistors in the comparator circuit. This substitution enables the use of digital logic operations instead of analog signal processing, resulting in faster conversion speeds and reduced power consumption while maintaining the comparator's core function of comparing input signals with reference signals
2Speed
If analog transistors are used in comparators, then the circuit can handle continuous analog signals, but operation speed becomes slow
Solution Approach 1:
The patent substitutes digital transistors for analog transistors, enabling the comparator to operate at digital switching speeds while maintaining signal conversion accuracy through precise digital comparison logic and controlled charge sharing mechanisms
Solution Approach 2:
The patent implements periodic sampling and comparison operations where the comparator processes signals in discrete time intervals. This periodic operation allows digital transistors to achieve high speeds while maintaining accuracy through controlled comparison cycles
3Productivity
If a large number of comparators are used for parallel processing, then signal conversion capacity increases, but vertical fixed-pattern noise increases
Solution Approach 1:
The patent replaces analog comparators with digital comparator circuits, which process signals through digital logic operations. This substitution reduces vertical fixed-pattern noise while maintaining parallel processing capacity, as digital circuits exhibit better matching and lower noise characteristics
Solution Approach 2:
The patent changes the operational parameters of the comparator by using digital transistors with optimized threshold voltages and switching characteristics. This parameter change enables parallel processing with reduced noise while maintaining the required signal conversion capacity
Data Source
AI summary
A system and method is provided for image sensing. The image sensing system includes a comparator for comparing an input signal representing a sensed light signal from at least one pixel of the image sensing system and a reference signal. The comparator includes at least one digital transistor.