BioFET Logarithmic Current-to-Time Readout for Linear Signals
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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, and existing digital compensation methods require complex designs 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, allowing for analog readout and eliminating the need for analog-to-digital conversion, thereby addressing the nonlinearity and dynamic range issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If bioFETs are operated in subthreshold regions, then power consumption is reduced, but the output signals become nonlinear and difficult to read
Solution Approach 1:
The patent applies parameter changes by transforming the output signal from the time domain to the frequency domain through Fourier transformation. This changes the representation parameters of the signal, allowing nonlinear subthreshold signals to be analyzed and processed in a linearized frequency spectrum, thereby resolving the contradiction between low power consumption and signal linearity
Solution Approach 2:
The patent introduces an intermediary processing stage (Fourier transformation and frequency domain analysis) between the bioFET output and the final measurement. This intermediary transforms the difficult-to-read nonlinear time-domain signals into analyzable frequency-domain representations, enabling accurate measurement while maintaining subthreshold operation
2Measurement precision
If digital compensation methods are used to address nonlinearity, then measurement precision is improved, but device complexity and chip area increase
Solution Approach 1:
The patent substitutes complex digital compensation circuits with a signal processing approach based on Fourier transformation. Instead of using additional hardware components for digital compensation, the solution uses mathematical transformation of the existing signal, thereby improving measurement precision without increasing device complexity or chip area
Solution Approach 2:
The patent creates a frequency domain copy of the time-domain signal through Fourier transformation. This copy allows for easier analysis and compensation of nonlinearities without requiring additional physical components, thus improving measurement precision while maintaining simple device architecture
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 low power consumption, reduced chip area requirements, and improved signal linearity, enabling efficient and cost-effective biosensor systems with expanded input dynamic ranges.
Implementation Method 1
A logarithmic current-to-time converter is used to convert exponential current signals from bioFETs into linear time domain signals
Data Source
AI summary
A bio-field effect transistor (bioFET) system includes a bioFET configured to receive to a first voltage signal and output a current signal, where the current signal varies exponentially with respect to the first voltage 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.