Photoelectric Conversion Apparatus Parallel Readout Circuit
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Solution Overview
Problem
The existing photoelectric conversion apparatus faces limitations in readout operations, including restricted high-speed signal reading and potential image quality degradation due to characteristic variations among amplification transistors in pixels, leading to noise generation in signals.
Innovation Solution
The apparatus incorporates a configuration with a first and second differential pair, where the first differential pair consists of a pixel transistor and a differential transistor, and the second differential pair includes a transistor that selectively activates or deactivates to improve the degree of freedom in signal readout, allowing parallel AD conversion and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single differential amplifier is used for signal readout, then the circuit structure is simple, but the readout speed is limited and cannot perform parallel AD conversion
Solution Approach 1:
The patent divides the readout function into multiple independent differential amplifiers (first and second differential amplifiers), each capable of independently performing AD conversion. This segmentation enables parallel processing of signals from different pixels, thereby increasing readout speed without requiring a single complex amplifier to handle all signals sequentially.
Solution Approach 2:
The third transistor is designed to selectively constitute different differential pairs (first or second differential pair) based on control signals. This multi-functionality allows a single transistor to participate in multiple operational modes, enabling the circuit to perform both parallel AD conversion and flexible signal routing, thus improving readout speed while controlling circuit complexity.
2Measurement precision
If amplification transistors are used in pixels, then signal amplification is achieved, but characteristic variations among transistors generate noise in signals
Solution Approach 1:
The patent implements a feedback mechanism where the third transistor selectively switches between different differential pairs based on signal characteristics. This allows the system to compensate for transistor characteristic variations by routing signals through optimal paths and performing correlated double sampling, thereby reducing noise while maintaining signal accuracy.
Solution Approach 2:
The patent changes the operational parameters of the differential amplifiers by selectively activating different transistor pairs. By dynamically adjusting which differential pair is active based on signal requirements, the system can optimize for either noise reduction or speed, thereby improving measurement precision while managing the harmful effects of transistor variations.
3Productivity
If parallel AD conversion is implemented, then readout speed increases, but the circuit complexity increases
Solution Approach 1:
The patent merges multiple functions into a unified circuit structure where the third transistor serves both the first and second differential pairs. This consolidation allows parallel AD conversion capability while sharing common circuit elements, thereby increasing productivity without proportionally increasing overall circuit complexity.
Solution Approach 2:
The patent introduces dynamic control mechanisms where the third transistor can selectively switch between different differential pairs based on real-time signal requirements. This dynamic reconfigurability enables the circuit to perform parallel AD conversion when needed while maintaining flexibility to reduce active circuit elements, thus improving productivity while managing complexity through adaptive operation.
Data Source
AI summary
The photoelectric conversion apparatus according to an embodiment includes a photoelectric conversion element (PD), a first transistor (Mpx) including a gate that receives a first signal from the photoelectric conversion element (PD), a second transistor (M2), and a third transistor (M3) that selectively constitutes a first differential pair constituted by the first transistor (Mpx) and the third transistor (M3) and a second differential pair constituted by the second transistor (M2) and the third transistor (M3). The photoelectric conversion apparatus outputs a second signal based on a voltage at the gate of the first transistor (Mpx) to a gate of the second transistor (M2).