Photo Sensing Unit With Threshold Voltage Differentiation
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Solution Overview
Problem
Traditional photo sensing units require multiple independent signal sources, increasing power consumption due to the need for separate control signals for photo sensing and switching transistors.
Innovation Solution
A photo sensing unit design where the threshold voltage of the photo sensing transistor is higher than the switching transistor, allowing the gates of both transistors to share a signal source, reducing the number of required signal sources and enabling power saving by using a write voltage lower than both threshold voltages during exposure and a readout voltage between the threshold voltages during readout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate signal sources are used for photo sensing transistor and switching transistor, then independent control is achieved, but power consumption increases
Solution Approach 1:
The patent merges the control signals for the photo sensing transistor and switching transistor into a single shared signal source. By setting the threshold voltage of the photo sensing transistor higher than that of the switching transistor, one signal source can independently control both transistors through voltage level differentiation, eliminating the need for separate signal sources and reducing power consumption.
Solution Approach 2:
The patent changes the threshold voltage parameter of the photo sensing transistor to be higher than that of the switching transistor. This parameter modification enables a single signal source to differentiate between controlling the photo sensing transistor and the switching transistor, achieving independent control without requiring separate signal sources.
2Use of energy by moving object
If a single signal source is shared by both transistors, then power consumption is reduced, but control independence is lost
Solution Approach 1:
The patent applies local quality by creating different control characteristics for different parts of the circuit through threshold voltage differentiation. The photo sensing transistor and switching transistor have different threshold voltages, allowing the single signal source to provide locally differentiated control - low voltage levels control the switching transistor while high voltage levels control the photo sensing transistor, maintaining control independence despite using a shared signal source.
3Device complexity
If threshold voltage of photo sensing transistor is made higher than switching transistor, then single signal source control is enabled, but transistor design complexity increases
Solution Approach 1:
The patent modifies the threshold voltage parameter during transistor design and manufacturing. By adjusting the doping concentration, gate oxide thickness, or channel width during fabrication, the photo sensing transistor is designed with a higher threshold voltage than the switching transistor, enabling single signal source control while using standard manufacturing techniques.
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 reduces power consumption by minimizing the number of signal sources needed, while effectively storing and outputting photo-induced electrical charges.
Implementation Method 1
The photo sensing transistor receives a light signal for inducing a photo current correspondingly
Implementation Method 2
The storage capacitor stores electrical charges induced by the light signal
Data Source
AI summary
A photo sensing unit used in a photo sensor includes a photo sensing transistor, a storage capacitor, and a switching transistor. The photo sensing transistor receives a light signal for inducing a photo current correspondingly, and a source and a gate thereof are respectively coupled to the first signal source and the second signal source. The storage capacitor stores electrical charges induced by the light signal, one terminal thereof is coupled to drain of the photo sensing transistor, and another terminal thereof is coupled to a low voltage. The switching transistor is controlled by the second signal source for outputting a readout signal from the storage capacitor to the signal readout line. The threshold voltage of the photo transistor is higher than that of the switching transistor.