Pixel Sample-and-Hold Feedback Circuit for kTC Noise Reduction
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Solution Overview
Problem
Existing solid-state imaging apparatuses face challenges in reducing kTC noise during pixel signal sampling, which degrades signal-to-noise ratio (S/N) in low illuminance conditions and limits dynamic range.
Innovation Solution
Incorporating a negative feedback circuit with a sample and hold circuit that feeds back a feedback signal based on the difference between the pixel signal and the output signal from the sample and hold circuit, effectively reducing kTC noise by applying negative feedback to both reset and signal components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a sample and hold circuit is used to sample the pixel signal, then the pixel signal can be held for readout, but kTC noise is generated during sampling which degrades the S/N ratio in low illuminance
Solution Approach 1:
The patent applies negative feedback by connecting the output of the sample and hold circuit back to its input through a feedback path. This feedback mechanism continuously adjusts the sampling process to minimize the difference between the input pixel signal and the held output signal, thereby reducing kTC noise generation while maintaining the signal holding capability.
2Device complexity
If no noise reduction measures are taken during pixel signal sampling, then the circuit design is simpler, but there is a large amount of kTC noise making it difficult to improve S/N in low illuminance
Solution Approach 1:
The patent introduces a feedback connection from the sample and hold circuit output back to its input, creating a negative feedback loop. This feedback mechanism reduces kTC noise by continuously correcting the sampling process, achieving noise reduction with relatively simple circuit modification rather than complex noise filtering systems.
3Object-affected harmful factors
If a negative feedback circuit is used to reduce kTC noise during pixel reset, then reset noise is reduced, but the signal component of the pixel signal cannot be negatively feedbacked
Solution Approach 1:
The patent extends the negative feedback mechanism to cover both the reset phase and the signal readout phase. By connecting the feedback path from the sample and hold circuit output back to its input, the system can apply negative feedback during both reset operations and signal sampling, thereby reducing kTC noise for both reset and signal components universally.
Data Source
AI summary
A solid-state imaging apparatus includes a pixel circuit that outputs a pixel signal and a negative feedback circuit. The negative feedback circuit includes a sample and hold circuit (hereinafter “SH circuit”) that samples and holds the pixel signal, and a feedback amplifier that negatively feeds back, to the SH circuit, a feedback signal according to a difference between the pixel signal from the pixel circuit and an output signal from the SH circuit.