Pixel Circuit Current-Sink Layout for Stable Low-Noise Sensing
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Solution Overview
Problem
Existing pixel circuits in electronic devices experience output variations due to connections with other circuits, leading to unstable and noisy sensing data.
Innovation Solution
The implementation of a pixel circuit design incorporating a photoelectric sensing element, multiple transistor devices, and pre-trap transistor devices, along with controlled current flows and signal periods, stabilizes the output by minimizing carrier conduction instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel circuits are connected to other circuits for readout and processing, then the pixel circuit can output sensing data, but the connected circuits will affect the sensing data and cause output variations
Solution Approach 1:
The pixel circuit is segmented into functionally independent modules: photoelectric sensing element for light detection, transistor devices for signal processing, and capacitor devices for charge storage. This segmentation isolates the sensing function from the readout circuitry, preventing external circuit influences from affecting the sensed signal while maintaining output capability.
Solution Approach 2:
Capacitor devices are introduced as intermediary elements between the photoelectric sensing element and the external readout circuits. These capacitors store the sensed charge temporarily, acting as a buffer that isolates the sensitive sensing node from voltage variations and loading effects of connected circuits, thereby maintaining output stability.
2Reliability
If multiple transistor devices are added to control current flow and reduce output variations, then the output stability is improved, but the device complexity increases
Solution Approach 1:
The transistor devices in the pixel circuit are designed to perform multiple functions: M1 and M2 serve as both switching elements for controlling signal readout and as active load elements for signal amplification. This multi-functionality reduces the need for additional dedicated components, maintaining output stability without proportionally increasing device complexity.
Solution Approach 2:
The circuit merges the functions of signal amplification, charge transfer control, and reset operations into a compact arrangement of transistors and capacitors. The transistor network is designed so that the same elements participate in multiple operational phases (exposure, readout, reset), effectively combining multiple control functions into a unified circuit structure.
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
The solution reduces output variation factors, ensuring stable and low-noise sensing data by maintaining a fixed voltage difference through transistor saturation, thereby enhancing the reliability of pixel circuit performance.
Implementation Method 1
Photoelectric sensing elements of the pixel circuits are exposed to sense lights and generate photodiode currents in response to incident lights
Data Source
AI summary
An electronic device including a plurality of sensing pixel circuits is provided. At least one of the sensing pixel circuits includes a photoelectric sensing element, a first transistor device, a second transistor device, a third transistor device and a fourth transistor device. The fourth transistor device includes a first end, a second end and a control end. The first end of the fourth transistor device is coupled to a first end of the first transistor device. The second end of the fourth transistor device is coupled to a bias voltage. The control end of the fourth transistor device is coupled to a scan line. The fourth transistor device serves as a current sink in a pre-trap period.