Temperature Sensing Circuit With Intrinsic Resistance Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Modern integrated circuits face errors in temperature measurement due to intrinsic resistances in transistors, which affect the accuracy of temperature sensing, reference voltage generation, and reference current generation.
Innovation Solution
A circuit design that utilizes multiple transistors with inherent base and emitter resistances, where specific current levels are applied to cancel out the effects of these resistances, allowing for accurate temperature measurement without requiring additional information about the resistances or current gain values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If base resistance and emitter resistance are present in bipolar transistors, then the transistor structure is realistic and manufacturable, but temperature measurement accuracy deteriorates due to errors in ΔVBE calculation
Solution Approach 1:
The patent extracts and removes the harmful effect of base resistance and emitter resistance from the temperature measurement equation by applying specific current ratios. By using current sources with carefully selected ratios, the resistance terms are mathematically eliminated from the ΔVBE calculation, leaving only the temperature-dependent terms that provide accurate measurement.
Solution Approach 2:
The patent changes the operating parameters (current ratios) to optimize the measurement. By selecting specific current ratios for the current sources, the equation transforms from one containing resistance errors to one where resistance terms cancel out, converting a problematic parameter situation into an optimal measurement condition.
2Measurement precision
If multiple current sources with specific ratios are used to cancel resistance effects, then temperature measurement accuracy improves, but circuit complexity increases
Solution Approach 1:
The patent makes the current sources serve multiple functions: they provide the necessary excitation for temperature measurement while simultaneously acting as error-cancellation mechanisms. The same current sources that drive the transistors also generate the voltage differences needed to eliminate resistance effects, reducing the need for separate compensation circuits.
Solution Approach 2:
The patent introduces current ratio relationships as an intermediary mechanism to bridge the gap between the physical transistor parameters and the ideal temperature measurement equation. The current ratios act as a mediating factor that transforms the problematic resistance-containing equation into an accurate temperature measurement equation without requiring direct modification of the transistor structure.
3Reliability
If base resistance is present in the transistor, then the transistor model is realistic, but the temperature sensing application becomes unreliable due to error introduction
Solution Approach 1:
The patent converts the harmful effect of base resistance into a beneficial outcome by using it as part of the measurement mechanism. The same base resistance that introduces error in conventional measurements becomes irrelevant when specific current ratios are applied, as its effect cancels out mathematically, transforming a harmful factor into a non-issue.
Solution Approach 2:
The patent applies preliminary anti-action by pre-calculating and pre-setting the current ratios to counteract the expected resistance effects before measurement occurs. The current sources are configured in advance with ratios that will precisely cancel the resistance terms in the measurement equation, preventing error introduction rather than correcting it after the fact.
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
The circuit achieves accurate temperature sensing by simplifying the voltage equations, eliminating errors introduced by intrinsic resistances, and providing precise temperature readings without needing additional resistance or current gain data.
Implementation Method 1
A common way to measure the temperature in integrated circuits is to make use of the temperature dependence of the voltage drop across diodes.
Implementation Method 2
Different currents may be successively applied to the diode, resulting in different VBE values across the diode. The ΔVBE values thus obtained may be successively integrated.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
In one embodiment, a circuit includes at least one transistor with a base and collector being electrically connected to a ground, and at least one current source being configured to apply four different currents (A, B, C, and D) to the emitter. A sum of the currents A and C are substantially equivalent to a sum of the currents B and D, or a sum of the currents A and D are substantially equivalent to a sum of the currents B and C. The circuit outputs first, second, third, and fourth voltage potentials between the emitter and the base during application of the currents A, B, C, and D, respectively.