Shift Register Pulse Output Circuit With Leakage-Resistant Channel Layout
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Solution Overview
Problem
Driver circuits with transistors of the same conductivity type can experience unstable operation due to leakage currents, leading to malfunctions in pulse signal output circuits and shift registers.
Innovation Solution
A pulse signal output circuit design where the channel length of transistors is optimized to reduce leakage currents, with at least one transistor having a multi-gate structure and using oxide semiconductors to enhance stability and mobility, and the inclusion of capacitors to maintain node potentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If transistors of the same conductivity type are used in driver circuits, then manufacturing simplicity is improved, but operation stability deteriorates due to leakage currents
Solution Approach 1:
The patent applies different channel lengths to different transistors within the same conductivity type. Specifically, the first transistor has a longer channel length than the second transistor, creating local structural differences that serve different functional purposes. This allows the circuit to maintain manufacturing simplicity while achieving operational stability through targeted leakage current reduction in specific circuit locations.
Solution Approach 2:
The patent changes the channel length parameter of transistors to control leakage currents. By making the first transistor's channel length longer than the second transistor's channel length, the patent reduces leakage current in specific circuit paths without requiring transistors of different conductivity types, thus maintaining manufacturing simplicity while improving operation stability.
2Reliability
If channel length of transistors is increased to reduce leakage currents, then operation stability is improved, but device area increases
Solution Approach 1:
The patent selectively increases channel length only for the first transistor where leakage current reduction is most critical, rather than uniformly increasing channel lengths of all transistors. This localized approach reduces leakage currents to improve operation stability while minimizing the overall device area increase.
Solution Approach 2:
The patent applies channel length extension partially - only to the first transistor and not equally to all transistors. This partial action is sufficient to reduce leakage currents and stabilize operation without the excessive area increase that would result from uniformly increasing all transistor dimensions.
Data Source
AI summary
An object of the present invention is to provide a pulse signal output circuit capable of operating stably and a shift register including the pulse signal output circuit. In an embodiment of the pulse signal output circuit, a transistor has a source terminal or a drain terminal connected to a gate electrode of another transistor having a source terminal or a drain terminal forming an output terminal of the pulse signal output circuit, the channel length of the transistor being longer than the channel length of the other transistor. Thereby, the amount of a leakage current modifying the gate potential of the other transistor can be reduced, and a malfunction of the pulse signal output circuit can be prevented.