Sub-Threshold MOSFET Temperature Sensing With Voltage Difference Readout
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Solution Overview
Problem
Existing temperature sensors face challenges in size and energy efficiency, particularly in applications like wearable devices and IoT devices, where they need to measure ambient or internal component temperatures while being compact and energy-efficient.
Innovation Solution
A semiconductor-based temperature sensor using a metal-oxide semiconductor field-effect transistor (MOSFET) operating in a sub-threshold region, coupled with a capacitor and an operational amplifier, performs temperature measurements by determining the voltage difference between gate-to-source voltages across successive measurement cycles, with an analog-to-digital converter converting the signal for control purposes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional temperature sensors are used to ensure accurate temperature measurement, then measurement precision is improved, but device size and power consumption increase
Solution Approach 1:
The patent changes the operating parameters of the MOSFET by utilizing sub-threshold voltages and specific bias current ratios (n:1 ratio between first and second bias currents) to enable temperature measurement through voltage difference detection rather than conventional current measurement, reducing power consumption while maintaining measurement accuracy
Solution Approach 2:
The patent replaces conventional temperature sensing mechanisms with a semiconductor-based voltage difference measurement system using MOSFETs operating in sub-threshold region, where temperature is measured through voltage differences rather than traditional electrical resistance or thermocouple methods, achieving lower power consumption
2Measurement precision
If conventional temperature sensors are used to ensure accurate temperature measurement, then measurement precision is improved, but device area increases
Solution Approach 1:
The patent merges the temperature sensing function with standard MOSFET circuitry that can be integrated into existing semiconductor processes, combining temperature measurement capabilities with conventional transistor operations rather than requiring separate dedicated sensor structures
Solution Approach 2:
By changing to sub-threshold operation mode and using voltage difference measurement with capacitive coupling, the patent achieves accurate temperature measurement with smaller device dimensions compared to conventional sensors that require larger structures for equivalent precision
3Use of energy by moving object
If the transistor operates in sub-threshold region to reduce power consumption, then energy efficiency is improved, but measurement precision may deteriorate
Solution Approach 1:
The patent introduces a capacitor as an intermediary element to store and compare voltage differences, enabling accurate temperature measurement through capacitive coupling and voltage comparison even when the MOSFET operates in the sub-threshold region with low currents
Solution Approach 2:
The operational amplifier provides feedback to accurately detect and amplify the small voltage differences between the first and second gate-to-source voltages, ensuring measurement precision is maintained despite the low-signal conditions in sub-threshold 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
This solution enables a compact and energy-efficient temperature sensor that can accurately measure temperatures and generate control signals for devices, suitable for various applications including wearable and IoT devices, with a linear relationship between temperature and voltage difference.
Implementation Method 1
The capacitor may be configured to store a first gate-to-source voltage of the transistor during a first phase of a measurement cycle
Implementation Method 2
The operational amplifier may be configured to determine a voltage difference between the first gate-to-source voltage stored in the capacitor and a second gate-to-source voltage of the transistor during a second phase of the measurement cycle, the voltage difference corresponding to a temperature of the transistor
Data Source
AI summary
An apparatus may include a transistor, a capacitor, and an operational amplifier. The transistor may have a sub-threshold voltage applied to a gate of the transistor. The capacitor configured to store a first gate-to-source voltage of the transistor while a first switch and a second switch are closed and a third switch is open. The capacitor may be charged to a first gate-to-source voltage of the transistor while the transistor is biased with a first bias current. The operational amplifier may be configured to determine a voltage difference between the first gate-to-source voltage stored in the capacitor and a second gate-to-source voltage of the transistor while the transistor is biased with a second bias current. The operational amplifier may determine the voltage difference while the third switch is closed and the first switch and the second switch are open. The voltage difference may correspond to a temperature of the transistor.