Amplifier Bias Decoupling for Low-Noise Multi-Channel Circuits

Solution Overview

Problem

Low noise amplifiers used in x-ray and CT scan equipment face challenges in minimizing circuit noise, particularly due to contributions from biasing and feedback resistors, leading to increased dosage requirements and crosstalk across multiple channels.

Innovation Solution

An amplifier circuit that employs a passive biasing source and an active biasing source, where the active source energizes the passive source and is selectively decoupled from it during signal amplification to isolate the amplifier from electronic noise, ensuring the desired bias signal is maintained without noise interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If an LNA biasing circuit is shared among multiple channels to reduce circuit area and power consumption, then power consumption and circuit area are reduced, but crosstalk and correlated noise increase across the multiple channels

Engineering Contradiction:

Improvepower consumptionVSAvoidcrosstalk and correlated noise

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The biasing circuit is segmented into separate biasing sources for each amplifier channel. Each amplifier has its own dedicated passive biasing source that is independently energized, preventing noise coupling between channels while maintaining the low-power benefits of passive biasing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A decoupler circuit is introduced as an intermediary between the active biasing source and the passive biasing source. This decoupler isolates the amplifier from noise generated by the active biasing source while still allowing the passive biasing source to provide the desired bias signal.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Area of stationary object

If an LNA biasing circuit is shared among multiple channels to reduce circuit area, then circuit area is reduced, but crosstalk and correlated noise increase across the multiple channels

Engineering Contradiction:

Improvecircuit areaVSAvoidcrosstalk and correlated noise

Core Design Contradiction:

Area of stationary objectVSObject-generated harmful factors

Solution Approach 1:

The biasing circuit is segmented into separate biasing sources for each amplifier channel. Each amplifier has its own dedicated passive biasing source that is independently energized, preventing noise coupling between channels while maintaining the low-power benefits of passive biasing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The active biasing source serves multiple functions: it energizes the passive biasing sources for multiple amplifiers during calibration, and can be selectively decoupled during signal amplification. This multi-functional approach reduces overall circuit complexity while maintaining channel isolation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Object-generated harmful factors

If relatively large, high power consuming transistors and BiCMOS devices are used to achieve low noise biasing, then noise performance is improved, but power consumption and cost increase

Engineering Contradiction:

Improvecircuit noiseVSAvoidpower consumption

Core Design Contradiction:

Object-generated harmful factorsVSUse of energy by moving object

Solution Approach 1:

A decoupler circuit is introduced as an intermediary between the active biasing source and the passive biasing source. This decoupler isolates the amplifier from noise generated by the active biasing source while still allowing the passive biasing source to provide the desired bias signal.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The biasing circuit transitions between different operational states: during calibration the active biasing source energizes the passive sources, and during signal amplification the decoupler isolates the amplifiers from the active source. This dynamic parameter change allows low-noise performance without continuous high power consumption.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7489191B2Circuit and method for reducing bias noise in amplifier circuits

Publication Date: 2009.02.10 GE PRECISION HEALTHCARE LLC

AI summary

An amplifier circuit and method for reducing bias noise is disclosed. The amplifier circuit includes a passive biasing source for supplying a desired bias signal to the amplifier and an active biasing source for energizing the passive biasing source to supply the desired bias signal. The amplifier circuit also includes a decoupler for selectively decoupling the active biasing source from the passive biasing source when the amplifier is configured for amplifying an input signal so that the amplifier remains isolated from electronic noise produced by the active biasing source while still being supplied the desired bias signal by the passive source.