MOS Current Generation Circuit for Accurate Differential Current

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Solution Overview

Problem

Existing current generation circuits in sensor devices face inaccuracies in generating differential currents due to variations in manufacturing processes of elements, leading to error components in the input currents, which result in a large error in the generated differential current.

Innovation Solution

A current generation circuit utilizing a first and second resistor connected to external circuits, along with amplifier circuits and MOS transistors, where the amplifier circuits control the injection of differential currents by applying output voltages to the gates of the transistors, eliminating the need for correcting base currents and reducing errors caused by manufacturing process variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If bipolar transistors are used to generate differential current, then the circuit can determine current difference, but base current errors and manufacturing process variations cause large errors in the generated differential current

Engineering Contradiction:

Improvedifferential current accuracyVSAvoidcurrent generation accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces bipolar transistors with MOS transistors in the current generation circuit. MOS transistors were selected because they do not have base current, eliminating the need for base current correction circuits and reducing the impact of manufacturing process variations on current accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the transistor type parameter from bipolar to MOS, which fundamentally alters the electrical characteristics by eliminating base current. This parameter change resolves the accuracy issue by removing the source of error components in the differential current generation.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If additional resistors and bipolar transistors are added to correct base current, then base current correction is achieved, but the circuit complexity increases and manufacturing variations still cause errors

Engineering Contradiction:

Improvebase current correctionVSAvoidcircuit structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts and removes the base current correction circuitry (additional resistors and bipolar transistors) by using MOS transistors that inherently do not require such correction. This eliminates the complex correction paths while maintaining current accuracy.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

By substituting bipolar transistors with MOS transistors, the patent eliminates the need for base current correction circuits, thereby simplifying the overall circuit structure without compromising measurement precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If elements in current paths have similar characteristics, then differential current generation is accurate, but manufacturing process variations cause differences in resistance values leading to error components

Engineering Contradiction:

Improvedifferential current accuracyVSAvoidelement characteristic consistency

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent substitutes bipolar transistors with MOS transistors, which have gate currents that are several orders of magnitude smaller than base currents. This substitution reduces the impact of manufacturing process variations on current path characteristics and minimizes error components in the differential current.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 configuration allows for the accurate generation of differential currents by controlling the current value injected, minimizing errors to only deviations in resistance values, thereby increasing the accuracy of the differential current between the input currents.

Implementation Method 1

a first amplifier circuit including a first positive input terminal to which the potential generated in the first resistor is supplied, and a first negative input terminal to which the potential generated in the second resistor is supplied; and a first MOS transistor having a gate connected to an output terminal of the first amplifier circuit

Methodology Applied

Scientific EffectVoltage control of current: Electrical Resistance

Data Source

PatentUS11249504B2Current generation circuit

Publication Date: 2022.02.15 ABLIC INC

AI summary

Provided is a current generation circuit including a first terminal to be connected to a first external circuit; a second terminal to be connected to a second external circuit; a first resistor in which a potential is generated by the first external circuit connected through the first terminal; a second resistor in which a potential is generated by the second external circuit connected through the second terminal; a first amplifier circuit including a first positive input terminal to which the potential generated in the first resistor is supplied, and a first negative input terminal to which the potential generated in the second resistor is supplied; and a first MOS transistor having a gate connected to an output terminal of the first amplifier circuit, a source connected to the first negative input terminal, and a drain connected to a first differential current terminal.