Pixel Circuit Layout With Shared Holding and Switching Transistors
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Solution Overview
Problem
Existing active matrix display devices require multiple elements in their pixel circuits to perform specific functions, which can lead to increased pixel size and costs.
Innovation Solution
A light emitting device with a reduced number of elements in its pixel circuit, comprising a light emitting element, driving and switching transistors, a writing transistor, and a holding transistor, where the holding transistor is configured to maintain the gate-source voltage of the driving transistor, and all transistors are formed in the same impurity region with the same conductivity type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple elements are used in the pixel circuit to perform specific functions, then the reliability and functionality are improved, but the pixel size and manufacturing cost increase
Solution Approach 1:
The patent merges the holding transistor and switching transistor into the same impurity region, allowing both transistors to share common structural elements (source, drain, and impurity region). This integration reduces the total area occupied by these transistors in the pixel circuit while maintaining their distinct electrical functions, directly addressing the contradiction between functionality and pixel size.
Solution Approach 2:
The holding transistor is designed with dual functionality: it holds the gate-source voltage of the driving transistor during the non-emission period and acts as a switching transistor during the emission period. This multi-functionality reduces the need for separate dedicated switching elements, thereby reducing pixel size while maintaining circuit reliability.
2Reliability
If multiple elements are used in the pixel circuit to perform specific functions, then the reliability and functionality are improved, but the manufacturing cost increases
Solution Approach 1:
By combining the holding transistor and switching transistor in the same impurity region, the patent reduces the total number of discrete elements that need to be manufactured and assembled. This integration simplifies the manufacturing process, reduces material usage, and lowers production costs while maintaining the necessary circuit functions.
Solution Approach 2:
The holding transistor's dual role as both a holding element and switching element reduces the total component count in the pixel circuit. Fewer components mean simpler manufacturing processes, reduced assembly steps, and lower overall production costs while maintaining full circuit functionality.
3Reliability
If the holding transistor and switching transistor are formed in different impurity regions with different conductivity types, then their individual functions are optimized, but the pixel size and manufacturing complexity increase
Solution Approach 1:
The patent merges the holding transistor and switching transistor into the same impurity region, reducing the structural complexity of the pixel circuit. By sharing common source, drain, and impurity region structures, the design simplifies the overall device architecture while maintaining the distinct electrical characteristics and functions of each transistor through appropriate gate control.
Data Source
AI summary
Alight emitting device includes a light emitting element, a driving transistor and a switching transistor each arranged on a path where a current for causing the light emitting element to emit light flows, a writing transistor arranged on a path connecting a signal line to which a pixel signal is supplied and a gate of the driving transistor, and a holding transistor configured to hold a gate-source voltage of the driving transistor. Agate of the holding transistor is connected to the gate of the driving transistor. Each of a source and a drain of the holding transistor is connected to a source of the driving transistor. The holding transistor and the switching transistor are formed in a same impurity region. A conductivity type of the holding transistor is the same as a conductivity type of the driving transistor.