DA Converter Threshold Tuning for Process-Variation Accuracy
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Solution Overview
Problem
The accuracy of digital-to-analog (DA) converters in wireless communication apparatuses degrades due to variations in threshold voltages of transistors caused by manufacturing processes.
Innovation Solution
A DA converter with adjustable threshold voltage transistors, specifically using a SONOS (Silicon/silicon Oxide/silicon Nitride/silicon Oxide/poly Silicon) structure, allows for precise adjustment of threshold voltages through electron injection and extraction, ensuring consistent conversion accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional transistors with fixed threshold voltages are used in the DA converter, then the circuit structure remains simple, but the conversion accuracy degrades due to manufacturing process variations
Solution Approach 1:
The patent applies dynamics by making the threshold voltage of transistors adjustable rather than fixed. The SONOS structure enables dynamic threshold voltage control through electron injection and extraction, allowing the DA converter to compensate for manufacturing variations and maintain high conversion accuracy while managing circuit complexity through controlled adjustability.
Solution Approach 2:
The patent changes the threshold voltage parameter of transistors to improve conversion accuracy. By controlling the threshold voltage of adjustment transistors through electron injection/extraction in the SONOS structure, the system can optimize performance and compensate for process variations without fundamentally changing the circuit topology.
2Measurement precision
If threshold voltages are made adjustable to improve accuracy, then conversion precision improves, but the device complexity increases
Solution Approach 1:
The SONOS structure provides dynamic threshold voltage adjustment capability, allowing the transistor to adapt its characteristics based on operational requirements. This dynamic control mechanism enables precise threshold voltage tuning to improve conversion precision while maintaining a relatively compact transistor structure compared to alternative approaches.
Solution Approach 2:
The patent uses a composite material structure (SONOS: Silicon/silicon oxide/silicon nitride/silicon oxide/poly silicon) to achieve threshold voltage adjustability. This multi-layer composite structure enables electron injection and extraction control, providing the necessary functionality for precise threshold voltage management without excessive device complexity.
3Adaptability or versatility
If multiple special power supplies are used to adjust threshold voltages, then the threshold control flexibility improves, but the circuit size and power supply requirements increase
Solution Approach 1:
The patent applies universality by designing the threshold adjustment mechanism to operate with a single special power supply. The SONOS structure and associated circuitry are configured to provide flexible threshold voltage control for multiple transistors using one power supply source, reducing the number of power supply components while maintaining adequate control flexibility for the DA converter operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the accuracy of DA conversion by reducing errors in on-state currents, maintaining high reliability with a reduced circuit size and requiring only a single special power supply, thus improving the reliability and efficiency of the DA converter.
Implementation Method 1
allows for precise adjustment of threshold voltages through electron injection and extraction
Data Source
AI summary
In general, according to one embodiment, a DA converter configured to convert a digital signal comprising n (n>1) bits to an analog current to output the analog current from an output terminal, includes n voltage-current converters. Each of them corresponds to each bit of the digital signal and is configured to generate a current depending on the corresponding bit. A k-th (k is an integer of 0 to n−1) voltage-current converter includes a first transistor whose threshold voltage is adjustable. The first transistor includes a semiconductor substrate, a first diffusion region, a second diffusion region, an insulating film, a charge accumulating film, and a gate.