Sense Transistor Source Resistor for Accurate Load Current Sensing
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Solution Overview
Problem
The existing transistor arrangements face challenges in precisely measuring load current due to parasitic effects, which cause deviations in the current ratio between the sense and load transistors, especially as the size of the sense transistor decreases relative to the load transistor and with temperature variations.
Innovation Solution
A transistor arrangement is designed with a compensation resistor integrated in the semiconductor body, connected between the source region of the sense transistor cell and a second source node, using a doped semiconductor material to stabilize the current proportionality factor and minimize temperature-dependent variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the size of the sense transistor is decreased relative to the load transistor, then the measurement precision is improved, but the deviation of current ratio from size ratio increases due to parasitic effects
Solution Approach 1:
The patent introduces a compensation resistor with a specific temperature coefficient to counteract the parasitic effects in the sense transistor. By carefully selecting the resistance value and temperature coefficient of the compensation resistor, the current ratio accuracy is maintained across different temperature conditions, allowing the sense transistor to be scaled down without sacrificing measurement precision
Solution Approach 2:
The compensation resistor acts as an intermediary element that mediates between the sense transistor and the measurement circuit. It compensates for the parasitic effects by introducing an opposing temperature-dependent resistance change, thereby maintaining the proportionality between sense current and load current even when the sense transistor size is reduced
2Area of stationary object
If the size of the sense transistor is decreased relative to the load transistor, then the area occupied is reduced, but the manufacturing precision becomes more difficult to maintain
Solution Approach 1:
The patent uses the compensation resistor to change the electrical parameters of the sense transistor circuit, specifically compensating for threshold voltage shifts and other parasitic effects that become more significant in smaller transistors. This allows smaller sense transistors to achieve the same current ratio accuracy as larger ones would without compensation
3Adaptability or versatility
If temperature variations occur, then the operating conditions change, but the current ratio deviates from the size ratio
Solution Approach 1:
The compensation resistor is specifically designed with a temperature coefficient that opposes the temperature-dependent parasitic effects in the sense transistor. As temperature changes, the compensation resistor's resistance changes in a way that counteracts the threshold voltage shifts and other temperature-induced variations, maintaining accurate current measurement across a wide temperature range
Solution Approach 2:
The compensation resistor provides a form of passive feedback by automatically adjusting its resistance based on temperature changes. This creates a negative feedback mechanism that counteracts the temperature-induced deviations in the sense transistor's current ratio, maintaining measurement accuracy without requiring active control
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 precise measurement of load current by stabilizing the current proportionality factor and reducing temperature-induced variations, ensuring accurate current measurement across varying conditions.
Implementation Method 1
a compensation resistor connected between the source region of the at least one sense transistor cell and a second source node. The compensation resistor is integrated in the semiconductor body and includes a resistive conductor, wherein the resistive conductor includes a doped semiconductor material.
Data Source
AI summary
A transistor arrangement and an electronic circuit with a transistor arrangement are disclosed. The transistor arrangement includes: drift and drain regions arranged in a semiconductor body and connected to a drain node; at least one load transistor cell having a source region integrated in a first active region of the semiconductor body; at least one sense transistor cell having a source region integrated in a second active region of the semiconductor body; a first source node electrically coupled to the source region of the at least one load transistor cell; a second source node electrically coupled to the source region of the at least one sense transistor cell; and a compensation resistor connected between the source region of the at least one sense transistor cell and the second source node. The compensation resistor is integrated in the semiconductor body and has a resistive conductor which includes a doped semiconductor material.