Bipolar Temperature Sensor Using Dynamic Current Density Ratio
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Solution Overview
Problem
Conventional temperature sensors using bipolar transistors suffer from inaccuracies due to faulty current sources and mismatches between transistors, leading to unreliable temperature measurements.
Innovation Solution
A temperature sensor design that utilizes a single bipolar transistor to determine PTAT voltage, compensating for variations in current sources and transistor mismatches by calculating a current density ratio in real-time, based on load voltages generated by passing different currents through the transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional temperature sensors use two identical bipolar transistors with a fixed current density ratio, then the device complexity is reduced, but the measurement precision deteriorates due to transistor mismatches and current source variations
Solution Approach 1:
The patent implements dynamic element matching by sequentially switching between multiple pairs of bipolar transistors and multiple current density ratios during temperature measurement. This dynamic switching allows the system to average out mismatches and variations, improving measurement precision while maintaining manageable device complexity through time-multiplexed operation
Solution Approach 2:
The patent changes the current density ratio parameter dynamically by switching between multiple predetermined ratios (e.g., 2:1, 3:1, 4:1) applied to different bipolar transistor pairs. This parameter variation enables the system to compensate for manufacturing variations and drift, achieving high measurement precision without requiring perfectly matched transistors
2Measurement precision
If dynamic element matching technique is used with multiple current density ratios, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent employs periodic switching between multiple bipolar transistor pairs and current density ratios in a systematic sequence. This periodic action allows the system to collect multiple measurements under varying conditions and compute an averaged temperature value, achieving high precision while organizing the complexity into a manageable periodic pattern
Solution Approach 2:
The patent designs the temperature sensor to use multiple bipolar transistor pairs that can serve different current density ratio functions. Each transistor pair can operate with multiple current ratios, making the hardware universal and reducing the need for separate dedicated circuits for each measurement condition, thus controlling 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 approach enhances the accuracy of temperature sensing by eliminating errors caused by transistor mismatches and current source variations, ensuring precise temperature measurement and preventing IC damage.
Implementation Method 1
When a first current is passed through the bipolar transistor, the bipolar transistor outputs a first complementary-to-absolute-temperature (CTAT) voltage (e.g., a first base-emitter voltage)
Implementation Method 2
the first base current is passed through the load and results in the generation of a first load voltage across the load
Data Source
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AI summary
A temperature sensor includes a sensing element and a load. Multiple different currents pass through the sensing element in a sequential manner. Based on each current that passes through the sensing element, the sensing element outputs a complementary-to-absolute-temperature (CTAT) voltage and another current. Further, the currents that pass through the sensing element and the currents that the sensing element output separately pass through the load and result in the generation of multiple load voltages across the load. A current density ratio of the temperature sensor is determined based on the load voltages generated across the load. Further, a temperature value indicative of a temperature sensed by the temperature sensor is generated based on the current density ratio and the CTAT voltages outputted by the sensing element based on the different currents that pass therethrough.