Dual-TFT Temperature Sensing Circuit With Tunable Output Current
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Solution Overview
Problem
Existing temperature detection circuits in electrical devices have limited design flexibility to alter the temperature dependence of output signals, requiring additional circuitry to manage temperature changes and often lack variability in temperature response.
Innovation Solution
A circuit design utilizing two thin-film transistors (TFTs) with different temperature dependencies, where both TFTs receive the same gate voltage, allowing for a controlled output current that decreases with increasing temperature, enabling adjustable temperature dependence and application in temperature sensors and regulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional circuitry is used to reduce output current in response to temperature increase, then temperature regulation capability is improved, but device complexity increases
Solution Approach 1:
The patent merges the temperature sensing function and temperature regulation function into a single integrated circuit. The first TFT serves as both the sensing element and the control element that directly regulates output current based on temperature changes, eliminating the need for separate sensing and regulation circuitries.
Solution Approach 2:
The first TFT performs multiple functions simultaneously: it acts as a temperature sensor by detecting threshold voltage changes with temperature, and as a temperature regulator by controlling the output current of the second TFT based on the detected temperature, making the circuit multi-functional and reducing overall complexity.
2Measurement precision
If conventional temperature detection circuits are used, then temperature detection is achieved, but design freedom to alter temperature dependence is limited
Solution Approach 1:
The patent applies local quality by using two different TFTs with deliberately different temperature dependence characteristics. The first TFT has stronger temperature dependence for sensing, while the second TFT has weaker temperature dependence for current output, allowing the circuit to achieve both accurate temperature detection and adjustable temperature dependence in the output signal.
Solution Approach 2:
The invention enables parameter changes by allowing designers to select TFTs with different temperature coefficients and adjust their physical dimensions (width-to-length ratios) to achieve desired output characteristics. This provides flexibility in tailoring the temperature dependence of the output signal to specific application requirements.
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 design provides a highly configurable and efficient means to generate electrical signals indicative of temperature, suitable for temperature sensing and regulation, enhancing reliability and manufacturing yields in compact devices like wearable electronics.
Implementation Method 1
the first and second TFTs are configured such that a temperature dependence of the first TFT differs from a temperature dependence of the second TFT, such that an output current at the second TFT and the second drain is dependent on temperature
Data Source
AI summary
Apparatus for producing an electrical signal that is indicative of a temperature is disclosed, the apparatus comprising: a first thin-film transistor TFT comprising a first source, a first gate and a first drain, the first drain being configured to receive a reference current; and a second TFT comprising a second source, a second gate and a second drain, the first and second gates both being configured to receive the same gate voltage, wherein the first and second TFTs are configured such that a temperature dependence of the first TFT differs from a temperature dependence of the second TFT, such that an output current at the second TFT and the second drain is dependent on temperature. The temperature dependence of the output current can be controlled by selecting suitable design parameters for the first and second TFTs. A method of designing the apparatus to produce an output current with a target temperature dependence is also disclosed.