BioFET Subthreshold Readout with Linear Time-Domain Conversion

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Solution Overview

Problem

BioFETs operated in subthreshold regions produce nonlinear output signals, which are challenging to read due to narrow input dynamic ranges, requiring complex digital compensation methods and increased chip area.

Innovation Solution

A logarithmic current-to-time converter is used to convert exponential current signals from bioFETs into linear time domain signals, enabling analog readout and eliminating the need for nonlinear voltage signal processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If bioFETs are operated in subthreshold regions to reduce power consumption, then power usage is reduced, but the output signals become nonlinear and difficult to readout

Engineering Contradiction:

Improvepower consumptionVSAvoidsignal readout

Core Design Contradiction:

Use of energy by moving objectVSEase of operation

Solution Approach 1:

The patent changes the operating parameters of the bioFET by applying a specific gate voltage signal with controlled amplitude and duration. This parameter control enables the extraction of linear information from the subthreshold nonlinear current response, resolving the contradiction between low power operation and easy signal readout

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces complex digital compensation methods with a simplified analog measurement approach. By measuring the duration of current flow rather than processing nonlinear voltage signals, the system achieves linear readout without requiring complex digital signal processing circuits

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If complex digital compensation methods are used to handle nonlinear signals, then signal processing accuracy is improved, but chip area increases

Engineering Contradiction:

Improvesignal processing accuracyVSAvoidchip area

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the essential information needed for measurement by controlling the gate voltage to produce a current pulse whose duration directly indicates the analyte concentration. This extraction approach eliminates the need for complex digital compensation circuits, reducing chip area while maintaining measurement precision

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses a simple, temporary current pulse measurement approach rather than permanent complex compensation circuits. The measurement is completed in a single pulse event, allowing for simpler hardware that does not require extensive digital processing infrastructure

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Measurement precision

If nonlinear voltage signals are processed, then accurate analyte detection is achieved, but the input dynamic range becomes narrow

Engineering Contradiction:

Improveanalyte detection accuracyVSAvoidinput dynamic range

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent uses periodic gate voltage pulses to probe the bioFET response. By controlling the pulse amplitude and duration, the system can measure analyte concentrations across a wide dynamic range while maintaining accurate detection through the linear relationship between pulse duration and analyte amount

Inventive Principle:

Principle #19Periodic action

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 approach results in a biosensor system with a wider input dynamic range, reduced power consumption, and simplified design, achieving linear signal processing without the need for analog-to-digital converters.

Implementation Method 1

a bioFET configured to receive a first voltage signal and output a current signal that varies exponentially with respect to the first voltage signal

Methodology Applied

Scientific EffectField-effect transistor operation:

Implementation Method 2

A logarithmic current-to-time converter connected to the bioFET and configured to receive the current signal and convert the current signal to a time domain signal that varies logarithmically with respect to the current signal

Methodology Applied

Scientific EffectLogarithmic conversion:

Data Source

PatentUS11614421B2BioFET system

Publication Date: 2023.03.28 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A bio-field effect transistor (bioFET) system includes a bioFET configured to receive a first voltage signal and output a current signal. A logarithmic current-to-time converter is connected to the bioFET and is configured to receive the current signal and convert the current signal to a time domain signal. The time domain signal varies logarithmically with respect to the current signal, such that the time domain signal varies linearly with respect to the first voltage signal.