Comparator Circuit With Positive Feedback and Current Limiting
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Solution Overview
Problem
In solid-state imaging devices, comparators in pixel columns face challenges in achieving high determination speed while maintaining low power consumption due to limited circuit accommodation area, leading to increased power consumption and reduced performance.
Innovation Solution
Incorporating a comparator with a comparison unit, a positive feedback circuit to enhance transition speed, and a current limiting unit to control current after inversion, along with a storage unit to store and output code signals, effectively reducing power consumption and increasing determination speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the comparator is designed to increase determination speed, then the determination speed is improved, but power consumption increases
Solution Approach 1:
The comparator circuit dynamically adjusts its operating state by switching between high-speed mode (during comparison) and low-power mode (after inversion). The positive feedback circuit is activated only during the transition period to boost speed, while the current limiting unit engages after inversion to reduce power consumption, making the circuit's characteristics adaptable to different operational phases.
Solution Approach 2:
The comparator operates in periodic cycles of high-current comparison phases followed by low-current standby phases. The positive feedback circuit provides periodic current boosting only when needed for transitions, while the current limiting unit enforces periodic current reduction after each comparison cycle completes, creating a rhythm of high-performance and low-power states.
2Area of stationary object
If the comparator circuit area is reduced to fit in pixel columns, then area efficiency is improved, but determination speed decreases
Solution Approach 1:
The positive feedback circuit is pre-configured and ready to activate immediately when the comparison result inverts. By having the feedback path and additional current sources pre-positioned in the compact circuit layout, the circuit eliminates delays that would occur if these speed-enhancing elements needed to be activated or configured during the comparison process.
Solution Approach 2:
The positive feedback circuit creates a regenerative effect that amplifies the comparison output signal during transitions. This feedback mechanism allows the compact comparator to achieve higher determination speeds by reinforcing its own output state changes, compensating for the speed limitations that would normally result from reduced circuit area.
3Speed
If the comparator is designed for high determination speed, then the determination speed is improved, but device complexity increases
Solution Approach 1:
The positive feedback circuit and current limiting unit are integrated into the comparator's core structure rather than being separate external components. The feedback path merges with the existing output stage, and the current limiting unit is combined with the differential pair structures, creating a unified compact design that achieves high speed without proportionally increasing overall device complexity.
Solution Approach 2:
The enhanced speed characteristics are localized to specific critical regions of the comparator circuit - particularly at the output stage where the positive feedback is applied and at the differential pairs where current limiting is implemented. This localized optimization allows the rest of the comparator to maintain simpler structures, balancing overall device complexity with targeted performance improvements.
Data Source
AI summary
The present disclosure relates to a comparator, an AD converter, a solid-state imaging device, an electronic apparatus, and a comparator control method that can reduce power consumption while increasing the determination speed of the comparator. The comparator includes a comparison unit, a positive feedback circuit, and a current limiting unit. The comparison unit compares the voltage of an input signal and the voltage of a reference signal, and outputs a comparison result signal. The positive feedback circuit increases the transition speed at the time when the comparison result signal is inverted. The current limiting unit limits the current flowing in the comparison unit after the inversion of the comparison result signal. The present disclosure can be applied to comparators, for example.