MOS Device Assembly with Segmented Gate Lengths
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Solution Overview
Problem
Existing MOS transistor designs have limited flexibility in transconductance characteristics, making it challenging to achieve uniform transconductance across different gate voltage ranges, which can lead to undesirable effects on circuit performance and increased complexity due to the need for additional DC blocks for isolation.
Innovation Solution
A MOS device assembly comprising multiple transistors with varying gate dimensions, such as different oxide thicknesses, gate lengths, and threshold voltages, all connected through a single poly gate, allowing for uniform transconductance when biased with the same voltage, thereby improving transconductance characteristics without relying solely on circuit design techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the gate length of a transistor is varied to adjust transconductance, then the transconductance of that transistor is improved, but the uniformity of transconductance across the transistor arrangement deteriorates
Solution Approach 1:
The transistor arrangement is segmented into multiple transistors with different gate lengths (e.g., 50nm, 65nm, 80nm, 100nm). Each transistor contributes a different transconductance value, and when combined in parallel, they create a composite transconductance characteristic that remains substantially uniform over a wide gate voltage range, resolving the contradiction between individual transistor optimization and overall uniformity.
Solution Approach 2:
Each transistor in the arrangement has locally optimized gate length dimensions tailored to specific transconductance requirements. The first transistor has a first gate length, the second transistor has a second gate length different from the first, and this pattern continues. This local differentiation in gate length creates complementary transconductance characteristics that collectively achieve uniform overall performance.
2Power
If differential biasing is used to achieve constant transconductance, then transconductance performance is improved, but device complexity increases due to isolation requirements
Solution Approach 1:
Multiple transistors with different gate lengths are merged into a single transistor arrangement that shares common source and drain regions. This consolidation eliminates the need for separate DC biasing circuits and isolation blocks for each transistor, reducing device complexity while maintaining the uniform transconductance performance achieved through the different gate length configurations.
Solution Approach 2:
The transistor arrangement with multiple gate lengths serves multiple functions simultaneously: it provides uniform transconductance over a wide voltage range, eliminates the need for separate DC blocks, reduces chip area, and simplifies the biasing network. This multi-functionality resolves the contradiction by achieving performance improvement without the associated complexity penalty.
3Stability of the object's composition
If extra primitive devices are added for DC block isolation, then transconductance uniformity is improved, but chip area increases
Solution Approach 1:
The transistor arrangement merges multiple transistors into a compact structure with shared source and drain regions, eliminating the need for separate DC block isolation devices. This consolidation maintains transconductance uniformity through the different gate length configurations while significantly reducing the chip area that would be required for separate isolation components.
Data Source
AI summary
A MOS device assembly having at least two transistors, each transistor having a gate region. The dimensions of the gate region of the first transistor are different from the dimensions of the gate region of the second transistor. The transconductance of the MOS device assembly is substantially uniform when the gate regions of the first and second transistors are biased using the same voltage.