Output Buffer Variable Resistance Tuning Across Process Fluctuations
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Solution Overview
Problem
The adjustable range of resistance values in existing semiconductor devices with variable resistance circuits is limited, making it difficult to set the resistance value to a predetermined value due to fluctuations in manufacturing processes and temperature.
Innovation Solution
The semiconductor device incorporates multiple replica circuits and operational amplifiers to control the gate voltage of transistors, allowing for a wider adjustable range of resistance values by using multiple sets of resistance elements and transistors, ensuring the resistance value can be accurately set despite manufacturing and temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single replica circuit and operational amplifier are used to control the variable resistance circuit, then the device complexity is low, but the adjustable range of resistance value is small
Solution Approach 1:
The variable resistance circuit is divided into M sets of parallel branches, where each branch contains a resistance element and a transistor. Each branch can be independently controlled by its own replica circuit and operational amplifier, allowing the total resistance to be adjusted through different combinations of branch conductances. This segmentation enables a wider adjustable range while maintaining manageable complexity through modular design.
Solution Approach 2:
The invention uses M operational amplifiers that dynamically adjust the gate voltages of M transistors based on feedback from M replica circuits. This dynamic control allows the system to adapt the resistance value continuously within a wide range by varying the conductance of individual branches, resolving the contradiction between wide adjustability and device complexity.
2Reliability
If the resistance value of the resistance element fluctuates due to manufacturing process and temperature, then the reliability of the circuit is affected, but using a wider adjustable range increases device complexity
Solution Approach 1:
Each of the M replica circuits provides feedback to its corresponding operational amplifier, creating closed-loop control for each parallel branch. This feedback mechanism compensates for resistance element fluctuations caused by manufacturing variations and temperature changes, ensuring that the combined resistance of the M branches can be accurately maintained at a predetermined value despite individual component variations.
Solution Approach 2:
The invention changes the conductance parameter of each transistor in the M parallel branches through voltage control. By adjusting the gate voltage of each transistor independently via its operational amplifier, the system can compensate for resistance fluctuations and achieve a stable predetermined resistance value, balancing reliability improvement with acceptable device complexity.
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
This solution significantly expands the adjustable range of resistance values, enabling precise adjustment and maintaining stability across varying conditions, thereby overcoming the limitations of existing technologies.
Implementation Method 1
a variable resistance circuit (terminating resistance element) including a first resistance element and a first transistor coupled in parallel
Implementation Method 2
an operational amplifier controlling gate voltage of the first and second transistors so that voltage across the terminals of the replica circuit becomes predetermined voltage
Data Source
AI summary
The present invention provides a semiconductor device in which an adjustable range of a resistance value of a variable resistance circuit is large. The semiconductor device has an output buffer including a plurality of sets of resistance elements and a plurality of sets of transistors, a plurality of replica circuits, and a plurality of sets of operational amplifiers, and drain currents of the plurality of sets of transistors are adjusted so that output impedances of the output buffer become predetermined values. Therefore, even in the case where the resistance values of the resistance elements largely fluctuate due to fluctuations in manufacture process and the like, the output impedances can be set to predetermined values.