Pixel Architecture Common Control Terminal Switching
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Solution Overview
Problem
Solid-state image sensors suffer from parasitic current leakages and parasitic light sensitivities, which affect their performance and efficiency.
Innovation Solution
The design incorporates a pixel configuration with a photodiode, transfer transistor, reset transistor, source follower transistor, and select transistor, along with a floating diffusion node, to manage charge transfer and reset operations efficiently, reducing parasitic currents and light sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pixel configurations are used, then image capture functionality is achieved, but parasitic current leakages and parasitic light sensitivities occur
Solution Approach 1:
The pixel is divided into distinct functional regions with separate transfer and reset transistors. The transfer transistor (first switch) and reset transistor (second switch) are segmented to perform specific functions independently, allowing precise control of charge transfer while minimizing parasitic effects in each region.
Solution Approach 2:
A floating diffusion node is introduced as an intermediary between the photodiode and the readout circuitry. This intermediate node facilitates charge transfer while isolating the photodiode from direct connection to subsequent stages, thereby reducing parasitic current pathways and light sensitivity issues.
2Reliability
If more transistors and circuit elements are added to reduce parasitic effects, then performance improves, but device complexity increases
Solution Approach 1:
The control terminals of the transfer transistor and reset transistor are connected to a common node, merging control functionality. This shared control mechanism reduces the number of independent control lines while maintaining the ability to independently operate both transistors for charge transfer and reset operations.
Solution Approach 2:
The pixel circuit is designed with multi-functional elements where the floating diffusion node serves both as charge storage during transfer and as the output node for readout. The shared control node provides universal control capability for both transfer and reset operations, reducing overall circuit complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the performance of image sensors by minimizing parasitic currents and light sensitivities, improving the overall efficiency and accuracy of image capture.
Implementation Method 1
Pixel circuitry is comprised of a photodiode
Data Source
AI summary
In accordance with an embodiment, a pixel includes at least two switches, each switch having a control terminal and first and second current carrying terminals. The control terminals of the first and second switches are commonly connected together. In accordance with another embodiment, a method for transferring charge from a first switch to a capacitance includes applying voltage to the commonly connected control terminals of the first and second switches.