Light-Emitting Transistor Circuit With Gate-Capacitor Compensation
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Solution Overview
Problem
Display devices using light-emitting elements face issues with variations in transistor characteristics, leading to inconsistent luminance due to threshold voltage and mobility variations, which affect the quality and uniformity of images displayed.
Innovation Solution
A semiconductor device structure incorporating a transistor, wiring, and capacitors to correct drain current variations by controlling the voltage applied between the source and gate of the transistor, allowing for stable operation even with normally-off transistors and reducing the number of transistors and wirings required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If transistors with different conductivity types are used to correct threshold voltage variations, then luminance uniformity is improved, but device complexity and manufacturing steps increase
Solution Approach 1:
The patent changes the electrical parameters of existing n-channel transistors by adjusting gate voltages and utilizing capacitor connections to achieve threshold voltage compensation, rather than introducing p-channel transistors. This parameter adjustment approach maintains luminance uniformity while avoiding the complexity of dual-conductivity-type transistor structures.
Solution Approach 2:
The patent extracts the threshold voltage compensation function from a separate p-channel transistor structure and integrates it into the existing n-channel transistor circuit through capacitor connections and gate voltage control, eliminating the need for complementary transistor pairs while maintaining the compensation effect.
2Manufacturing precision
If additional transistors and capacitors are added to correct drain current variations, then image quality is improved, but the number of components and wirings increases
Solution Approach 1:
The patent makes existing circuit components serve multiple functions: the gate electrode serves both as a control terminal and as a threshold voltage compensation node, while capacitors serve both as charge storage elements and as compensation mechanisms. This multi-functionality reduces the need for additional dedicated compensation components.
Solution Approach 2:
The patent merges the threshold voltage compensation function with the existing drive transistor circuit by connecting capacitors to the gate and utilizing gate voltage control, combining what would traditionally be separate compensation circuits into the main transistor structure, thereby reducing total component count.
3Ease of manufacture
If conventional transistor structures are used, then manufacturing is simpler, but variations in threshold voltage cause luminance inconsistencies
Solution Approach 1:
The patent implements preliminary threshold voltage compensation by pre-charging capacitors connected to the gate electrode before the transistor operates. This preliminary action sets the gate voltage to account for threshold voltage variations, ensuring consistent luminance output without requiring complex real-time adjustment mechanisms.
Solution Approach 2:
The patent implements a feedback mechanism where capacitors connected to the gate electrode sense and compensate for threshold voltage variations. The capacitor charge/discharge cycles provide feedback that automatically adjusts the gate voltage to maintain consistent drain current and luminance output despite transistor parameter variations.
Data Source
AI summary
A semiconductor device that is less influenced by variations in characteristics between transistors or variations in a load, and is efficient even for normally-on transistors is provided. The semiconductor device includes at least a transistor, two wirings, three switches, and two capacitors. A first switch controls conduction between a first wiring and each of a first electrode of a first capacitor and a first electrode of a second capacitor. A second electrode of the first capacitor is connected to a gate of the transistor. A second switch controls conduction between the gate and a second wiring. A second electrode of the second capacitor is connected to one of a source and a drain of the transistor. A third switch controls conduction between the one of the source and the drain and each of the first electrode of the first capacitor and the first electrode of the second capacitor.