Bandgap Voltage Reference Buffering for Low Amplifier Noise

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Solution Overview

Problem

Amplifying bandgap voltage references introduces unwanted circuit noise in integrated circuits, which detracts from achieving low noise designs.

Innovation Solution

Implementing a voltage reference circuit with a bandgap reference circuit, a unity gain buffer circuit, and optionally incorporating a PTAT and CTAT circuit, along with RC filtering to minimize noise contributions and eliminate amplifier gain noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If amplifier gain is increased to adjust reference output voltage, then voltage flexibility is improved, but circuit noise increases

Engineering Contradiction:

Improvereference output voltage flexibilityVSAvoidamplifier gain noise

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

Instead of using high-gain amplifiers to achieve voltage flexibility, the patent inverts the approach by using unity-gain buffers combined with adjustable voltage dividers. The voltage adjustment is achieved through passive component ratios rather than active amplification, thereby eliminating amplifier gain noise while maintaining flexibility.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent extracts the amplification function from the voltage reference circuit by using a unity-gain buffer, separating the voltage generation function from the voltage adjustment function. This allows the reference voltage to be generated with minimal noise and then adjusted independently using passive components.

Inventive Principle:

Principle #2Taking out (Extraction)

2Adaptability or versatility

If traditional amplifier circuits are used to amplify bandgap voltage reference, then output voltage flexibility is improved, but noise performance deteriorates

Engineering Contradiction:

Improveoutput voltage adjustment rangeVSAvoidnoise performance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent introduces a unity-gain buffer as an intermediary between the bandgap voltage reference and the output stage. This buffer acts as a mediator that provides voltage adjustment capability through its feedback network without introducing the noise associated with high-gain amplifiers, thus improving output flexibility while maintaining noise performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If amplifier gain is used to achieve different voltage levels, then device versatility is improved, but current consumption increases

Engineering Contradiction:

Improvevoltage level adjustmentVSAvoidamplifier current consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent replaces the expensive, high-power amplifier with a unity-gain buffer and passive voltage division network. These simpler components consume significantly less current while achieving the same voltage adjustment functionality, effectively trading off amplifier complexity for energy efficiency.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS20260044170A1Method for the design of low noise precision bandgap voltage references

Publication Date: 2026.02.12 ANALOG DEVICES INC

AI summary

A voltage reference circuit includes a bandgap voltage reference circuit, and an amplifier circuit including a first input coupled to an output of the bandgap voltage reference circuit and a second input directly coupled to an output of the amplifier.