Variable-Gain LNA Feedback Network for Stable Phase Across Gain Modes

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Solution Overview

Problem

Existing low noise amplifiers face challenges in miniaturization due to limited gain mode flexibility and phase compensation difficulties, leading to performance degradation as gain varies.

Innovation Solution

A variable gain low noise amplifier design incorporating stacked transistors, a negative feedback circuit with sub-negative feedback circuits, and phase compensation capacitors to provide adjustable resistance values and compensate for phase changes across different gain modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple cores are implemented for variable gain, then gain flexibility is improved, but the amplifier becomes bulky

Engineering Contradiction:

Improvegain flexibilityVSAvoidamplifier size

Core Design Contradiction:

Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The negative feedback circuit is divided into multiple sub-negative feedback circuits (first to nth sub-negative feedback circuits), each corresponding to a separate gain mode. This segmentation allows each sub-circuit to handle a specific gain range, achieving variable gain functionality without requiring multiple complete amplifier cores, thus reducing overall amplifier size while maintaining gain flexibility.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If gain is varied in typical LNA structures, then gain adaptability is improved, but phase compensation becomes difficult and performance degrades

Engineering Contradiction:

Improvegain adaptabilityVSAvoidphase stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The feedback circuit is segmented into multiple sub-circuits, each with its own phase compensation capacitor. This allows phase compensation to be optimized independently for each gain mode, maintaining phase stability across the full gain range while enabling gain adaptability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different resistance values are provided for different gain modes through the sub-negative feedback circuits. By changing the resistance parameter in each sub-circuit, the feedback gain is adjusted to compensate for phase changes that occur with gain variations, thereby maintaining phase stability across different gain settings.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a single feedback circuit is used, then circuit simplicity is maintained, but phase compensation for variable gain is insufficient

Engineering Contradiction:

Improvecircuit simplicityVSAvoidphase compensation accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Rather than using a single complex feedback circuit, the approach segments the feedback function into multiple simpler sub-circuits. Each sub-circuit is optimized for a specific gain mode, making the overall phase compensation more accurate while keeping individual sub-circuit designs relatively simple.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10826442B2Variable gain low noise amplifier with phase compensation

Publication Date: 2020.11.03 SAMSUNG ELECTRO MECHANICS CO LTD

AI summary

An apparatus includes an amplifying circuit configured to include stacked first and second transistors, and to amplify a signal input from an input terminal during an operation in an amplifying mode, and provide the amplified signal to an output terminal, and a negative feedback circuit comprising first to nth sub-negative feedback circuits, each corresponding to a separate gain mode included in the amplifying mode, wherein the negative feedback circuit is configured to provide a variable resistance value to determine a negative feedback gain based on each of the separate gain modes.