Impedance Tuning Apparatus Using Current Mirrors

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Solution Overview

Problem

Conventional impedance tuning apparatuses suffer from distorted comparison results due to input voltage offset of operation amplifiers and errors in reference resistors, leading to inaccurate impedance tuning, especially in Integrated Circuit (IC) forms.

Innovation Solution

The impedance tuning apparatus includes an operation amplifier, a reference resistor, a switching module, a current generator, a current detector, and a controller, where the switching module couples the endpoint to either the reference resistor or the tuned resistor based on a control signal, generating reference or tuned currents, and the current detector outputs current values to the controller for tuning the resistance value, eliminating input bias issues and avoiding voltage division-related distortions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If voltage comparison method is used with operation amplifiers, then impedance tuning can be performed, but comparison results are distorted due to input voltage offset

Engineering Contradiction:

Improveimpedance tuning accuracyVSAvoidinput voltage offset distortion

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the voltage comparison method with a current comparison method. Instead of using operation amplifiers to compare voltages (which suffer from input offset errors), the invention uses current mirrors and switching modules to compare currents directly. This substitution of the comparison mechanism eliminates the harmful effect of input voltage offset while maintaining the impedance tuning function.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces current mirrors as intermediary elements between the tuned resistor and the comparison mechanism. The current mirrors convert the voltage signals into current signals, allowing comparison without direct voltage measurement by operation amplifiers. This intermediary transformation eliminates the distortion caused by input voltage offset.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If reference resistors are used to generate reference voltages, then impedance tuning can be performed, but errors in reference resistors affect comparison accuracy

Engineering Contradiction:

Improvecomparison result accuracyVSAvoidreference resistor error sensitivity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the reference voltage generation method (using reference resistors) with a current mirror-based reference current generation method. The current mirrors provide a more stable and accurate reference that is less sensitive to component variations, thereby improving comparison result accuracy and reducing reference resistor error sensitivity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If voltage division circuits are used, then impedance comparison can be performed, but inaccurate resistance values cause distortion

Engineering Contradiction:

Improveimpedance comparison capabilityVSAvoidresistance value accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent replaces voltage division circuits with direct current comparison using switching modules and current mirrors. This eliminates the need for voltage division and its associated sensitivity to resistance value inaccuracies, maintaining ease of operation while significantly improving measurement precision.

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 solution ensures accurate impedance tuning by eliminating the impact of operation amplifier input bias and avoiding resistance value inaccuracies, resulting in improved tuning precision without the need for voltage division circuits.

Implementation Method 1

The current generator is coupled to the switching module, and receives and mirrors the reference current or the tuned current to generate a first current or a second current respectively

Methodology Applied

Scientific EffectCurrent mirroring:

Data Source

PatentUS8368458B2Impedance tuning apparatus

Publication Date: 2013.02.05 IC PLUS CORP

AI summary

An impendence tuning apparatus is disclosed. The impendence tuning apparatus includes an operation amplifier, a reference resistor, a tuned resistor, a switching module, a current generator, a current detector and a controller. A first input terminal of the operation amplifier receives a basic voltage and the second terminal of the operation amplifier coupled to a first end. The switching module receives a control and coupled the first end to the tuned resistor or the reference resistor accordingly for generating a tuned current or a reference current separately. The current generator receives and mirrors the reference current or the tuned current to generate a first current and a second current. The current detector receives the first and the second currents and outputs current values the first and the second currents to the controller. The controller tunes an impendence of the tuned resistor according to the first and the second currents.