LCD Driver Circuit Bootstrap Layout for Degraded Thin-Film Transistors
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Solution Overview
Problem
Transistors formed using non-single-crystal semiconductors in driver circuits for large display devices suffer from deterioration issues such as increased threshold voltage and reduced mobility, leading to operational failures and poor display quality.
Innovation Solution
A driver circuit design incorporating specific transistor configurations and connections, including a bootstrap transistor and switch transistors, to control potential differences and timing, thereby enhancing transistor performance and reducing channel width requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If transistors are formed using non-single-crystal semiconductors in driver circuits, then cost is reduced and manufacturing is simplified, but transistor deterioration occurs leading to increased threshold voltage and reduced mobility
Solution Approach 1:
A bootstrap transistor is introduced to preliminarily increase the potential of the gate of the pull-up transistor before the transistor performs its main function. This preliminary action compensates for the inherent deterioration of non-single-crystal semiconductor transistors by proactively adjusting the gate potential, thereby maintaining reliable operation despite the use of cost-effective non-single-crystal materials
2Reliability
If the channel width of transistors is increased to compensate for deterioration, then transistor performance is improved, but layout area increases
Solution Approach 1:
Instead of changing the physical dimension (channel width) to compensate for deterioration, the invention changes the electrical parameter (gate potential) by introducing the bootstrap transistor. This parameter change approach maintains transistor performance while avoiding the area penalty that would result from increasing channel width
3Loss of energy
If Vgs of the pull-up transistor is reduced to minimize power consumption, then power consumption is decreased, but on-resistance increases affecting signal quality
Solution Approach 1:
The bootstrap transistor acts as an intermediary that indirectly controls the gate potential of the pull-up transistor. This intermediary mechanism allows the system to maintain low power consumption while still achieving the necessary signal quality by precisely controlling when and how the gate potential is adjusted, rather than directly manipulating Vgs
Data Source
AI summary
A driver circuit includes first to third transistors, a first circuit, and a second circuit. In the first transistor, a first terminal is electrically connected to a second wiring, a second terminal is electrically connected to a first wiring, and a gate is electrically connected to the second circuit and a first terminal of the third transistor. In the second transistor, a first terminal is electrically connected to the first wiring, a second terminal is electrically connected to a sixth wiring, a gate is electrically connected to the first circuit and a gate of the third transistor. A second terminal of the third transistor is electrically connected to the sixth wiring. The first circuit is electrically connected to a third wiring, a fourth wiring, a fifth wiring, and the sixth wiring. The second circuit is electrically connected to the first wiring, the second wiring, and the sixth wiring.