BioFET Readout Using Logarithmic Current-to-Time 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, and existing digital compensation methods require complex designs and increased chip area.
Innovation Solution
The implementation of a logarithmic current-to-time converter that converts 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 limitations.
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:
A logarithmic current-to-time converter is introduced as an intermediary device between the bioFET and the readout system. This converter transforms the exponential current signal from the bioFET into a linear time-domain signal, making the signal easier to read while preserving the low-power operation of the subthreshold bioFET
Solution Approach 2:
The patent changes the parameter domain of the signal from current (exponential relationship) to time (linear relationship) through logarithmic conversion. This parameter transformation resolves the nonlinearity issue while maintaining the energy efficiency of subthreshold operation
2Measurement precision
If existing digital compensation methods are used, then nonlinearity can be compensated, but device complexity and chip area increase
Solution Approach 1:
The patent replaces complex digital compensation circuits with a simpler analog logarithmic current-to-time converter. This substitution achieves the same nonlinearity compensation function with reduced device complexity and smaller chip area by using analog signal processing instead of digital methods
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 solution enables linear signal processing, expanding the input dynamic range and reducing power consumption and design complexity, resulting in a more efficient and cost-effective biosensor system.
Implementation Method 1
A logarithmic current-to-time converter 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.
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.