Weak-Inversion MOS Thermistor Circuit for Temperature-Stable Current
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Solution Overview
Problem
Conventional electronic devices designed to withstand temperature variations require bulky and complex structures, leading to high development time, manufacturing costs, and large silicon surface area, making them inefficient and costly.
Innovation Solution
An electronic device with a compact structure comprising a thermistor and a current source, where the thermistor operates in weak inversion mode with a negative temperature coefficient drain-source resistor, and a current source coupled to the output terminal, producing an output voltage with a positive temperature coefficient, allowing for temperature detection and compensation with low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional temperature compensation structures (box package, thermal sensors, control modules, current source modules, biasing means) are used, then temperature stability is improved, but device complexity and silicon surface area increase
Solution Approach 1:
The patent combines the temperature sensing function and temperature compensation function into a single integrated circuit module. The module includes a first current source for temperature sensing and a second current source for temperature compensation, both implemented using standard CMOS transistors and resistors on the same silicon substrate. This merging eliminates the need for separate discrete components and complex packaging structures, thereby reducing device complexity while maintaining temperature stability.
Solution Approach 2:
The integrated circuit module serves multiple functions simultaneously: it acts as both a temperature sensor (detecting temperature through the first current source) and a temperature compensator (adjusting the second current source based on detected temperature). Additionally, the module provides biased current to external circuitry while maintaining temperature independence. This multi-functionality reduces the number of separate components needed, thereby reducing device complexity.
2Stability of the object's composition
If conventional temperature compensation structures are used, then temperature stability is improved, but manufacturing cost increases
Solution Approach 1:
By integrating temperature sensing, temperature compensation, and current biasing functions into a single CMOS-compatible circuit module, the patent enables all components to be manufactured using standard semiconductor fabrication processes. This eliminates the need for separate packaging, assembly, and testing of discrete components, thereby reducing manufacturing cost while maintaining temperature stability.
Solution Approach 2:
The patent uses standard CMOS transistors and resistors with well-controlled electrical parameters that can be precisely manufactured using conventional semiconductor processes. The temperature compensation mechanism relies on controlled variations in transistor operating parameters (such as threshold voltage and channel width) that are inherently manageable in CMOS fabrication, thereby reducing manufacturing cost compared to specialized components.
3Stability of the object's composition
If conventional temperature compensation structures are used, then temperature stability is improved, but silicon surface area increases
Solution Approach 1:
The patent integrates multiple functions (temperature sensing, temperature compensation, and current biasing) into a single compact circuit module occupying a small area on the silicon substrate. By combining these functions that would traditionally require separate discrete components and packaging, the patent achieves temperature stability while minimizing silicon surface area usage.
Solution Approach 2:
The circuit module employs a nested arrangement where the temperature sensing circuit (first current source) and temperature compensation circuit (second current source) are closely integrated and interlinked. The compensation circuit is effectively nested within the same functional block as the sensing circuit, sharing common substrates and interconnect structures, thereby minimizing the total silicon surface area required.
4Measurement precision
If a thermistor with MOS transistor in weak inversion mode is used, then temperature detection precision is improved, but power consumption decreases
Solution Approach 1:
The patent operates the MOS transistor in weak inversion mode, which is a specific operating region between cutoff and strong inversion. In this mode, the transistor exhibits high sensitivity to temperature changes due to the exponential relationship between gate voltage and drain current, thereby improving temperature detection precision. Simultaneously, the weak inversion operation inherently consumes very low power because the drain current is naturally suppressed, thus achieving both high precision and low power consumption.
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 enables stable performance across varying temperatures with a compact, low-power, and cost-effective design, using a single thermistor and current source, and a circuit that delivers an output current independent of temperature, reducing the need for complex modules and silicon area.
Implementation Method 1
a negative temperature coefficient drain-source resistor and the source of which is coupled to said output terminal
Implementation Method 2
a first MOS transistor configured to operate in weak inversion mode
Implementation Method 3
configured to deliver on said output terminal an output voltage with a positive temperature coefficient
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The electronic device includes a module (3) having an output terminal (BS), configured to deliver on said output terminal (BS) an output voltage (Vout) with a positive temperature coefficient, and comprising a thermistor (4) having a first MOS transistor (T1) configured to operate in low inversion mode and to have a drain-source resistance with a negative temperature coefficient and whose source (S1) is coupled to said output terminal (BS), and a current source (5) coupled to the output terminal (BS) and configured to impose the drain-source current (Ids1) of the first transistor (T1).