Adjustable Amplifier Circuitry for Image Sensor Readout Noise and Speed
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Solution Overview
Problem
Current image sensors face challenges in optimizing readout circuitry for varying light conditions, resulting in suboptimal performance in low light scenarios with high read noise and power consumption, and in high light scenarios where quick signal reading is necessary while minimizing power usage.
Innovation Solution
The implementation of adjustable readout circuitry with separate amplifier configurations and operational modes for low light and high light signals, allowing for optimized noise reduction, settling accuracy, and power management by adjusting transistor configurations and common mode voltages based on light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single amplifier configuration is used for both low light and high light signals, then device complexity is reduced, but low light signal quality deteriorates due to high read noise and high light processing efficiency deteriorates due to excessive power consumption
Solution Approach 1:
The patent divides the amplifier circuit into two separate configurations: a first amplifier for low light signals and a second amplifier for high light signals. This segmentation allows each amplifier to be optimized for its specific signal type, with the first amplifier configured for low noise operation and the second amplifier configured for high speed, low power operation, thereby resolving the contradiction between device complexity and measurement precision.
Solution Approach 2:
The patent implements dynamic switching between amplifier configurations based on light conditions. The readout circuitry can selectively activate the first amplifier configuration for low light signals and the second amplifier configuration for high light signals, allowing the system to adapt its characteristics to match the input signal requirements, thus improving both low light signal quality and high light processing efficiency.
2Device complexity
If a single amplifier configuration is used for both low light and high light signals, then device complexity is reduced, but power consumption increases during high light signal processing
Solution Approach 1:
The patent segments the amplifier functionality into two distinct configurations optimized for different operating conditions. The second amplifier configuration is specifically designed for high light signals with parameters optimized for low power consumption and high speed operation, preventing excessive power usage during high light processing while maintaining simplicity through a unified readout circuitry structure.
Solution Approach 2:
The patent changes key amplifier parameters depending on the light condition. For high light signals, the second amplifier configuration uses different gain, bandwidth, and power management parameters compared to the first amplifier, allowing optimization for low power consumption and high speed processing without requiring a completely separate circuit.
3Measurement precision
If amplifier circuitry is optimized for low light signals with high settling accuracy, then low light signal quality improves, but high light signal processing speed decreases
Solution Approach 1:
The patent creates two separate amplifier configurations with different performance characteristics. The first amplifier is optimized for high settling accuracy with higher gain and bandwidth suitable for low light signals, while the second amplifier is optimized for high speed processing with appropriate parameters for high light signals. This segmentation resolves the contradiction by providing the right amplifier for each signal type.
Solution Approach 2:
The patent changes amplifier parameters including gain, bandwidth, and settling time based on the input signal conditions. The first amplifier configuration uses parameters optimized for high settling accuracy to improve low light signal quality, while the second amplifier configuration uses different parameters optimized for fast processing of high light signals, eliminating the trade-off between accuracy and speed.
4Speed
If amplifier circuitry is optimized for high light signals with fast processing, then high light processing speed improves, but low light signal quality deteriorates due to increased noise
Solution Approach 1:
The patent segments amplifier functionality into two configurations where the first amplifier is specifically optimized for low light signals with parameters that minimize noise and maximize settling accuracy, while the second amplifier is optimized for high light signals with parameters that maximize processing speed. This segmentation allows each configuration to excel at its intended function without compromising the other.
Solution Approach 2:
The patent changes critical amplifier parameters such as gain, bandwidth, and noise filtering based on the light condition. The first amplifier configuration uses parameters optimized for low noise and high settling accuracy to preserve low light signal quality, while the second amplifier configuration uses parameters optimized for high speed processing of high light signals, resolving the contradiction between speed and signal quality.
Data Source
AI summary
An image sensor may include an array of image pixels. The array of image pixel may be coupled to column readout circuitry. A given image pixel may generate a low light signal and a high light signal for a given exposure. A column line may couple the given image pixel to readout circuitry having amplifier circuitry. The column line may be coupled to an autozeroing transistor for reading out the high light signal and a source follower stage for readout out the low light signal. The amplifier circuitry may receive different common mode voltage depending on whether it is amplifying the low or high light signal. The gain and other operating parameters of the amplifier circuitry may be adjusted based on whether it is amplifying the low or high signal. If desired, separate amplifier circuitry may be implemented for the low and high light signals.