MOSFET Distortion Compensation for Linear Output Current

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Solution Overview

Problem

MOSFET-based analog signal processing circuits often exhibit non-linear responses and distortion, which affect the accuracy of analog signal processing, particularly in integrated circuits that combine digital and analog signal processing.

Innovation Solution

An analog amplifier system comprising a transimpedance or voltage amplifier and a distortion compensator, where the distortion compensator generates a second distortion current with a lower transconductance to cancel out the first distortion current, thereby reducing or eliminating non-linear distortion in the output current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If MOSFETs are used in analog signal processing circuits, then space efficiency and low quiescent current are achieved, but non-linear response and distortion occur

Engineering Contradiction:

Improvequiescent currentVSAvoidsignal processing accuracy

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

A distortion compensator circuit is introduced as an intermediary component between the MOSFET amplifier and the output. This compensator generates a correction current that is injected into the amplifier output to cancel the distortion components, thereby maintaining signal accuracy while preserving the low quiescent current advantage of MOSFETs

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The distortion compensator exploits the non-linear characteristics of MOSFETs to generate a correction current that is equal in magnitude but opposite in phase to the distortion current. By converting the harmful distortion effect into a useful correction signal, the system eliminates distortion while maintaining the energy efficiency of MOSFET operation

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Manufacturing precision

If distortion compensator is added to reduce non-linear distortion, then signal processing accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvesignal processing accuracyVSAvoidcircuit complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The distortion compensator is designed to address only the specific non-linear distortion components generated by the MOSFET amplifier, rather than attempting to correct all possible signal imperfections. The compensator uses transistors with different aspect ratios to generate correction currents targeted at specific distortion harmonics, thereby achieving high signal accuracy with a relatively simple localized circuit

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS10998864B1Non-linearity correction

Publication Date: 2021.05.04 XILINX INC

AI summary

An apparatus for generating an output current including a first distortion current based on a first transconductance and a second distortion current based on a second transconductance is disclosed. The first distortion current may be generated by an amplifier and the second distortion current may be generated by a distortion compensator. The second transconductance may be less than the first transconductance. In some implementations, the second distortion current may reduce the first distortion current output by the apparatus.