BJT Temperature Sensor Bridge Circuit Mitigates IR Drop
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor temperature sensors face issues with signal-to-noise ratio, measurement resolution, and accuracy due to device mismatch, voltage drops, and parasitic resistance, which affect the reliability of temperature measurements.
Innovation Solution
The implementation of a symmetric bridge-like design using bipolar junction transistors (BJTs) with a series-coupled configuration and diode-connected transistors to measure temperature, where currents of equal magnitude flow through pairs of transistors, allowing for the measurement of voltage differences that are functions of temperature, thereby improving signal-to-noise ratio and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional semiconductor temperature sensors are used, then temperature measurement can be performed, but device mismatch, voltage drops, and parasitic resistance reduce measurement accuracy and signal-to-noise ratio
Solution Approach 1:
The patent employs asymmetric current paths through the bipolar junction transistors where different currents flow through different transistor branches. By deliberately creating asymmetric current distribution (I1 through Q1, I2 through Q2, etc.) while measuring voltage differences, the system exploits the temperature-dependent VBE characteristics to extract accurate temperature information while canceling out common-mode errors from parasitic resistances and device mismatches.
Solution Approach 2:
The patent introduces intermediate measurement nodes (nodes A, B, C, D) that serve as mediators between the transistor junctions and the measurement system. These intermediate nodes allow for differential voltage measurements that indirectly capture temperature information while rejecting the effects of parasitic resistances and power supply variations, thereby improving measurement reliability.
2Measurement precision
If conventional temperature sensors are used, then temperature sensing is achieved, but signal-to-noise ratio and measurement resolution are decreased due to parasitic resistance and voltage drops
Solution Approach 1:
The patent converts the harmful effects of parasitic resistances and voltage drops into beneficial measurement features. By measuring voltage differences between strategically selected nodes and using differential measurement techniques, the system causes parasitic voltage drops to appear as common-mode signals that are rejected in the differential measurement, thereby transforming these harmful factors into sources of measurement robustness.
Solution Approach 2:
The patent segments the temperature sensing function across multiple bipolar junction transistors (Q1, Q2, Q3, Q4) arranged in a bridge-like configuration. Each transistor contributes to the overall measurement, and by segmenting the measurement into multiple parallel paths with different current flows, the system achieves better signal-to-noise ratio through statistical averaging and error cancellation while maintaining high measurement resolution.
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 signal-to-noise ratio, measurement resolution, and reliability of temperature measurements by effectively mitigating the limitations of conventional sensors, providing more accurate temperature readings.
Implementation Method 1
Some conventional semiconductor temperature sensors function based on temperature dependence of VBE of a bipolar junction transistor (BJT) or a forward bias voltage of a p/n junction diode.
Data Source
AI summary
Temperature sensors using bipolar junction transistors are provided. Examples of the disclosed sensors minimize effects of IR drop and have improved accuracy. An example temperature sensor includes a first branch coupled between a power supply and ground. The first branch includes a first transistor series-coupled with a second transistor via a first node and has a first temperature sensor output via the first node. The temperature sensor also includes a second branch coupled between the power supply and ground. The second branch includes a third transistor series-coupled with a fourth transistor via a second node and has a second temperature sensor output via the second node. The first through fourth transistors are diode-connected and can have an n-well structure or a deep n-well structure. The temperature sensor also includes a voltage sensor having an input coupled to the first temperature sensor output and the second temperature sensor output.