High-Order Integrator Circuit With One Op-Amp for ΔΣ ADC SN Ratio

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Solution Overview

Problem

Conventional continuous-time delta-sigma (ΔΣ) A/D converters require an increased number of operational amplifiers to improve resolution and signal-to-noise (SN) performance, leading to increased circuit scale and power consumption, which is a bottleneck for mobile communications equipment.

Innovation Solution

A high-order integrator configuration using a single operational amplifier with specific filter structures, including serially-connected resistance and capacitance elements, allows for arbitrary transfer characteristics up to the (n−1)th order, reducing the need for multiple amplifiers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the filter order is increased to improve resolution and SN performance, then the signal-to-noise ratio is improved, but the number of operational amplifiers must be increased

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidnumber of operational amplifiers

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges multiple filter functions into a single operational amplifier by configuring multiple RC filter circuits (first filter with n resistance elements and n-1 capacitance elements, second filter with n capacitance elements and n-1 resistance elements) to share the same amplifier. This combining approach achieves high-order filtering (improving SN ratio) while using only one operational amplifier, thereby resolving the contradiction between measurement precision and device complexity.

Inventive Principle:

Principle #5Merging (Combining)

2Measurement precision

If the number of operational amplifiers is increased to improve resolution and SN performance, then the signal-to-noise ratio is improved, but the circuit scale is increased

Engineering Contradiction:

ImproveresolutionVSAvoidcircuit scale

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent combines multiple high-order filter circuits into a single operational amplifier structure. The first filter (with resistance elements R1-Rn and capacitance elements C1-Cn-1) and second filter (with capacitance elements C1'-Cn' and resistance elements R1'-Rn'-1) share the same amplifier, achieving high resolution through high-order filtering while minimizing circuit scale by eliminating the need for multiple separate amplifiers.

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If the number of operational amplifiers is increased to improve resolution and SN performance, then the signal-to-noise ratio is improved, but the power consumption is increased

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by stationary object

Solution Approach 1:

The patent merges multiple filter functions into a single operational amplifier, reducing the total number of active devices from multiple amplifiers to just one. This consolidation achieves the desired signal-to-noise ratio through high-order filtering while significantly reducing power consumption by eliminating redundant amplifier power draws.

Inventive Principle:

Principle #5Merging (Combining)

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 enables improved SN performance without increasing circuit scale or power consumption, making it suitable for mobile communications equipment.

Implementation Method 1

a first filter connected between an input terminal of the integrator and an inverted input terminal of the operational amplifier; and a second filter connected between the inverted input terminal and output terminal of the operational amplifier, wherein the first filter includes n (n is an integer equal to or more than 2) serially-connected first resistance elements, n−1 first capacitance elements each connected between each interconnecting node of the first resistance elements and a ground

Methodology Applied

Scientific EffectRC filtering: Filter (electronic)

Data Source

PatentUS8674864B2Integrator and oversampling A/D converter having the same

Publication Date: 2014.03.18 PANASONIC HOLDINGS CORP

AI summary

A high order integrator is configured using an operational amplifier, a first filter connected between an input terminal of the integrator and an inverted input terminal of the operational amplifier, and a second filter connected between the inverted input terminal and output terminal of the operational amplifier. The first filter includes n serially-connected first resistance elements, n−1 first capacitance elements each connected between each interconnecting node of the first resistance elements and the ground, and n−1 second resistance elements each connected between each interconnecting node of the first resistance elements and the ground. The second filter includes n serially-connected second capacitance elements, n−1 third resistance elements each connected between each interconnecting node of the second capacitance elements and the ground, and n−1 third capacitance elements each connected between each interconnecting node of the second capacitance elements and the ground.