Bias Generator Feedback Circuit for RF Amplifier Flicker Noise

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Solution Overview

Problem

Conventional amplifiers are susceptible to flicker noise, which increases as device feature sizes decrease, and existing methods to reduce flicker noise either require large R-C networks or increasing device sizes, both of which are impractical in many cases.

Innovation Solution

A flicker-compensated bias generator with a feedback circuit that generates a bias voltage based on a reference voltage and current, and subtracts a feedback current to attenuate flicker noise, effectively canceling it without the need for additional R-C networks or increasing device sizes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If device feature sizes are reduced to shrink amplifier size, then amplifier area is reduced, but flicker noise increases

Engineering Contradiction:

Improveamplifier areaVSAvoidflicker noise

Core Design Contradiction:

Area of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback circuit that samples the output of the bias generator and feeds it back to the input through a current sink. This feedback mechanism detects flicker noise components and actively cancels them by subtracting the feedback current from the reference current, thereby reducing flicker noise in the bias voltage without requiring larger device dimensions.

Inventive Principle:

Principle #23Feedback

2Object-affected harmful factors

If R-C networks are added to filter flicker noise, then flicker noise is reduced, but circuit area increases

Engineering Contradiction:

Improveflicker noiseVSAvoidcircuit area

Core Design Contradiction:

Object-affected harmful factorsVSArea of moving object

Solution Approach 1:

The patent replaces the conventional passive R-C filtering approach with an active feedback-based noise cancellation system. Instead of using resistors and capacitors to attenuate flicker noise, the invention uses operational amplifiers, current sources, and feedback circuits to actively detect and subtract noise components, achieving superior noise reduction with smaller area footprint.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If device sizes are increased to reduce flicker noise, then flicker noise decreases, but amplifier area increases

Engineering Contradiction:

Improveflicker noiseVSAvoiddevice area

Core Design Contradiction:

Object-affected harmful factorsVSArea of moving object

Solution Approach 1:

The patent converts the harmful effect of flicker noise into a measurable signal that can be cancelled. By sampling the bias generator output and feeding it back through a current sink, the system identifies flicker noise components and actively subtracts them from the reference current, transforming the noise problem into a controllable feedback signal that reduces overall noise without requiring larger devices.

Inventive Principle:

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

Data Source

PatentUS10666192B2Attenuation of flicker noise in bias generators

Publication Date: 2020.05.26 QUALCOMM INC

AI summary

This disclosure provides systems and apparatuses for reducing flicker noise in output signals provided by a radio frequency (RF) amplifier. In some implementations, the RF amplifier may include a bias generator to provide one or more bias signals to control operating points of devices and circuits of the RF amplifier. The bias generator may include a feedback circuit to generate a current to attenuate flicker noise within the bias generator. In some implementations, the feedback circuit may receive a bias voltage and may generate the current based on a frequency of the bias voltage.