Reference Current Circuit Without Op-Amp for Low Temperature Drift

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Solution Overview

Problem

Existing electronic circuits for generating a reference current with a low temperature coefficient are costly and inefficient due to the use of operational amplifiers, which consume significant circuit area and power.

Innovation Solution

An electronic circuit design that eliminates the operational amplifier, utilizing a configuration of transistors and resistors with matched temperature coefficients to generate a reference current, allowing the circuit to operate independently and at lower supply voltages, with the temperature coefficient of the reference current determined by the reference voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an operational amplifier is used to generate a reference current with low temperature coefficient, then the temperature coefficient of the reference current is improved, but the circuit area and power consumption increase significantly

Engineering Contradiction:

Improvetemperature coefficient of reference currentVSAvoidcircuit area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent extracts and removes the operational amplifier from the reference current generation circuit, replacing it with a simplified transistor-based current mirror configuration. This extraction eliminates the large area-consuming op-amp while maintaining the temperature compensation function through the transistor matching and resistor ratio design.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses current mirror technology to copy the reference current through matched transistors (M1-M4, M5-M6 pairs). The current mirror replicates the current while the resistor ratios (R1/R2, R3/R4) copy the temperature compensation characteristics, achieving the desired low temperature coefficient without the operational amplifier.

Inventive Principle:

Principle #26Copying

2Reliability

Engineering Contradiction:

Improvetemperature coefficient of reference currentVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by stationary object

Solution Approach 1:

The operational amplifier is extracted and removed from the circuit, eliminating its high power consumption. The replacement transistor-based current mirror consumes significantly less power while maintaining the temperature compensation function through careful selection of transistor parameters and resistor ratios.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the expensive, high-power operational amplifier with simpler, lower-cost transistor and resistor components. These simpler components achieve the same temperature compensation function at a fraction of the power cost, effectively using 'cheaper' components to replace the 'expensive' op-amp.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If an operational amplifier is used to generate a reference current, then the reference current generation is achieved, but the circuit complexity and cost increase

Engineering Contradiction:

Improvereference current generationVSAvoidcircuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The operational amplifier is extracted from the circuit, significantly reducing the device complexity. The reference current generation function is achieved through a simpler current mirror configuration with four transistors and four resistors, eliminating the need for the complex operational amplifier circuitry.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of using an operational amplifier to actively control and regulate the reference current, the patent inverts the approach by using passive transistor matching and resistor ratios to naturally establish the reference current. This inversion from active control to passive establishment simplifies the circuit architecture.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11966246B2Electronic circuit for generating reference current with low temperature coefficient

Publication Date: 2024.04.23 RICHTEK TECH

AI summary

An electronic circuit includes a first transistor coupled between a first node and a supply voltage and controlled by a first node, a second transistor coupled between a second node and the supply voltage and controlled by the first node, a third transistor coupled between a third node and the supply voltage and controlled by a fourth node, a fourth transistor coupled between the fourth node and the supply voltage and controlled by the fourth node, a fifth transistor coupled between the first node and the fifth node and controlled by a reference voltage, a sixth transistor coupled between the second node and a ground and controlled by the third node, a seventh transistor coupled between the fourth node and the ground and controlled by the second node, a first resistor coupled the fourth node to the ground, and a second resistor coupled to the fifth node.