Comparator Circuit With Switchable Voltage Drop for Auto-Zero Tuning
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Solution Overview
Problem
Current CMOS image sensors with single-slope type ADCs face challenges in easily modifying the auto-zero potential of comparators, which is crucial for optimal operation.
Innovation Solution
A comparator design that includes a differential pair, a current mirror, a voltage drop mechanism, and a switch, allowing for easy modification of the operating point potential by controlling the voltage drop between transistors, enabling flexible auto-zero potential adjustment without external voltage generation circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an externally applied voltage generation circuit is provided outside of the comparator to generate an externally applied voltage for modifying auto-zero potential, then the auto-zero potential can be modified, but the device complexity increases
Solution Approach 1:
The voltage drop mechanism is extracted from the external circuit and integrated directly into the comparator structure, specifically between the differential pair transistors. This integration eliminates the need for separate external voltage generation circuits while maintaining the auto-zero potential modification capability.
Solution Approach 2:
The voltage drop mechanism is merged with the comparator's internal transistor structure, combining the potential modification function with the existing differential pair architecture. This merging reduces the overall device complexity by eliminating separate external components.
2Ease of operation
If a voltage drop mechanism is integrated within the comparator between differential pair transistors, then the operating point potential can be easily modified without external circuits, but the transistor configuration becomes more complex
Solution Approach 1:
The voltage drop mechanism is applied locally between specific transistors in the differential pair rather than throughout the entire circuit. This localized approach enables precise operating point potential modification while minimizing the impact on the overall transistor configuration complexity.
Solution Approach 2:
The invention modifies the operating point potential by changing the voltage parameter through the integrated voltage drop mechanism. By adjusting the voltage drop characteristic, the auto-zero potential can be easily modified without requiring complex reconfiguration of the transistor network.
3Reliability
If the comparator maintains linearity during both normal and inversion changes in RAMP and VSL signals, then the operational stability improves, but the design constraints increase
Solution Approach 1:
The comparator design incorporates dynamic适应能力 to handle both normal and inversion changes in the RAMP and VSL signals. The integrated voltage drop mechanism allows the operating point to adapt dynamically, maintaining linearity across different signal conditions without requiring separate designs for each mode.
Solution Approach 2:
The comparator is designed with universal functionality to operate correctly under both normal and inversion signal conditions. The integrated voltage drop mechanism provides a unified solution that maintains linearity across different operating modes, reducing the need for mode-specific design constraints.
Data Source
AI summary
The present technology relates to a comparator that can easily modify operating point potential of the comparator, and an imaging device. A pixel signal output from a pixel, and, a reference signal with changeable voltage are input to a differential pair. A current mirror connected to the differential pair, and a voltage drop mechanism allowed to cause a predetermined voltage drop is connected between a transistor that configures the differential pair, and a transistor that configures the current mirror. A switch is connected in parallel to the voltage drop mechanism. The present technology can be applied, for example, to an image sensor that captures an image.