Temperature Sensor Circuit Compensating Nonlinear BJT Effects
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Solution Overview
Problem
Existing temperature sensor circuits face challenges in generating a consistently linear temperature-dependent signal across a wide operating temperature range due to nonlinear components such as the Early effect and high-level injection, making it difficult to achieve accurate temperature compensation without quantitatively estimating these nonlinear components.
Innovation Solution
A temperature sensor circuit design that uses two BJT pairs with different bias conditions and arithmetic operations between their temperature-dependent voltage signals to eliminate nonlinear components, generating a linearly proportional-to-absolute temperature (PTAT) signal without requiring digital-analog conversion, thereby simplifying circuit design and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor generates a temperature-dependent signal based on the base-emitter voltage difference of a BJT pair, then the signal is proportional to temperature, but nonlinear components (Early effect, high-level injection) cause deviations from linearity
Solution Approach 1:
The patent divides the temperature sensor into multiple BJT pairs, each operating at different bias conditions (different current densities). By segmenting the measurement into multiple operating points, the system can capture and compensate for nonlinear effects that would be present in a single operating point, thereby maintaining accuracy across a wider temperature range.
Solution Approach 2:
The patent changes the bias current parameters of the BJT pairs to operate at different current densities. By varying these parameters and measuring the temperature-dependent signals at multiple bias conditions, the system can differentiate and compensate for nonlinear components (such as Early effect and high-level injection) from the ideal PTAT signal, improving measurement accuracy.
2Measurement precision
If conventional technologies compensate for forward Early effect and reverse Early effect, then some nonlinearity is reduced, but accurate compensation requires quantitative estimation of nonlinear components which is very difficult
Solution Approach 1:
The patent implements a feedback mechanism where the temperature sensor measures its own output at multiple bias conditions, and the control circuit uses this information to automatically adjust and compensate for nonlinear effects. This closed-loop approach eliminates the need for external quantitative estimation of nonlinear components, simplifying the compensation process while maintaining high accuracy.
Solution Approach 2:
The temperature sensor system performs self-compensation by measuring its own characteristics at different operating points and using this information to correct for nonlinear effects. The system serves its own calibration needs without requiring external equipment or complex external compensation circuits, reducing overall system complexity.
3Measurement precision
If a temperature sensor is designed for high accuracy in analog applications, then compensation circuits are needed, but this increases device complexity and may not be suitable for digital applications
Solution Approach 1:
The patent designs a universal temperature sensor architecture that can serve both analog and digital applications. By implementing compensation through multiple BJT pairs with different bias conditions and using digital processing of the measured signals, the system achieves high accuracy for analog applications while also being compatible with digital interfaces and processing, eliminating the need for separate compensation circuits.
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 effectively compensates for nonlinear errors in the analog domain, reducing the need for additional digital processing and optimizing circuit performance across a wide temperature range, enhancing the accuracy and flexibility of temperature measurement in both analog and digital applications.
Implementation Method 1
A temperature sensor module circuit may include a first bipolar junction transistor pair and a second bipolar junction transistor pair
Data Source
AI summary
A temperature sensor circuit and a compensation method for the temperature sensor circuit are disclosed herein. The temperature sensor circuit may provide a proportional-to-absolute temperature (PTAT) output signal with a compensation scheme. The temperature sensor circuit includes a first temperature sensor module circuit, a second temperature sensor module circuit, and an arithmetic operation circuit. The first temperature sensor module circuit generates a first temperature voltage signal based on a first reference current level. The second temperature sensor module circuit generates a second temperature voltage signal based on a second reference current level. The arithmetic operation circuit generates an output signal as PTAT voltage signal using the first temperature voltage signal and the second temperature voltage signal, eliminating reverse Early effect and High-level injection effect with simple arithmetic operation.