Oxide Semiconductor Shift Register for Stable Pulse Output
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Solution Overview
Problem
Transistors including oxide semiconductors in driver circuits can lead to unstable operation due to the same conductivity type, affecting the stability of shift registers.
Innovation Solution
A pulse signal output circuit is designed with specific transistor configurations and ratios of channel width to length, utilizing oxide semiconductors, and incorporating capacitors and additional transistors to stabilize operation, including a shift register with multiple pulse signal output circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If transistors including oxide semiconductors are used in driver circuits, then field-effect mobility is improved, but operation stability deteriorates due to same conductivity type
Solution Approach 1:
The patent applies local quality by using oxide semiconductor transistors with different conductivity types (n-channel and p-channel) in different locations within the driver circuit. Specifically, the shift register includes both n-channel transistors (first transistor, sixth transistor) and p-channel transistors (second transistor, fifth transistor) positioned at different stages to perform different switching functions, thereby achieving stable operation while maintaining high mobility
Solution Approach 2:
The patent employs asymmetry by designing the pull-up transistor (second transistor, p-channel) and pull-down transistor (fifth transistor, p-channel) with different conductivity types and different W/L ratios. The p-channel transistors are strategically placed to counterbalance the n-channel transistors, creating an asymmetric circuit structure that achieves stable operation with oxide semiconductor materials
2Ease of manufacture
If oxide semiconductor films are formed at low temperature, then manufacturing process is simplified, but device performance may be compromised
Solution Approach 1:
The patent applies parameter changes by optimizing the W/L ratios of transistors with different conductivity types to compensate for the lower carrier mobility of p-channel oxide semiconductor transistors. The second transistor (p-channel) is designed with a larger W/L ratio than the first transistor (n-channel) to achieve balanced drive strength, thereby maintaining device performance despite low-temperature fabrication
3Device complexity
If shift register uses only n-channel transistors, then device complexity is reduced, but operation stability deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the shift register circuit into functional blocks with different transistor types. The circuit is segmented into pull-up networks (using p-channel transistors) and pull-down networks (using n-channel transistors), with each segment performing specific functions. This segmentation allows the circuit to achieve stable operation while maintaining reasonable complexity
Solution Approach 2:
The patent employs inversion by using p-channel transistors (second transistor, fifth transistor) in conjunction with n-channel transistors, essentially inverting the conventional approach of using only one conductivity type. This inversion strategy allows the circuit to achieve balanced pull-up and pull-down capabilities, resulting in stable operation
Data Source
AI summary
An object is to provide a pulse signal output circuit capable of operating stably and a shift register including the pulse signal output circuit. A pulse signal output circuit according to one embodiment of the disclosed invention includes first to tenth transistors. The ratio W/L of the channel width W to the channel length L of the first transistor and W/L of the third transistor are each larger than W/L of the sixth transistor. W/L of the fifth transistor is larger than W/L of the sixth transistor. W/L of the fifth transistor is equal to W/L of the seventh transistor. W/L of the third transistor is larger than W/L of the fourth transistor. With such a structure, a pulse signal output circuit capable of operating stably and a shift register including the pulse signal output circuit can be provided.