Liquid-Contact FET Gate Driving With On-Chip Feedback
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Solution Overview
Problem
Existing field-effect transistors (FETs) face challenges in maintaining stable and rapid detection of low concentrations of substances in fluidic environments due to chemical interactions with electrodes, leading to potential drifts and high time constants from resistances and capacitances, limiting their speed and accuracy.
Innovation Solution
A gate driver system utilizing on-chip metal electrodes and reference electrodes, such as Ag/AgCI, for precise control of gate voltage, enhancing feedback accuracy and reducing time constants through dual driving signals and feedback loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If reference electrodes (Ag/AgCl) are used to maintain stable potential, then stability is improved, but device complexity and response time worsen due to intrinsic resistances and capacitances
Solution Approach 1:
The patent extracts the reference electrode from the liquid environment and places it on the chip substrate. This removes the reference electrode from the harmful liquid environment, eliminating chemical interactions and potential drifts while maintaining its stabilizing function. The reference electrode is now part of the solid-state chip structure rather than being immersed in the liquid sample.
Solution Approach 2:
The patent introduces an intermediary structure - a dielectric layer with a hole - between the reference electrode and the liquid environment. This intermediary protects the reference electrode from direct contact with the liquid, preventing chemical reactions while still allowing the reference potential to be established. The hole in the dielectric layer serves as a controlled interface.
2Reliability
If reference electrodes are used to ensure stable potential, then reliability is improved, but speed worsens due to high time constants from resistances and capacitances
Solution Approach 1:
By extracting the reference electrode from the liquid environment and integrating it into the chip substrate, the patent eliminates the high resistance and capacitance pathways that existed when the reference electrode was immersed in the liquid. This dramatically reduces the time constant while maintaining the reliability benefits of a stable reference potential.
Solution Approach 2:
The patent replaces the traditional mechanical/chemical reference electrode system (immersed in liquid) with an integrated electronic system on the chip. This substitution transitions from a system limited by electrochemical time constants to one governed by faster electronic signal processing, thereby increasing response speed.
3Speed
If on-chip metal electrodes are used for drive and sense, then speed is improved by reducing time constants, but stability worsens due to lack of chemical stability
Solution Approach 1:
The patent merges the advantages of both on-chip metal electrodes and reference electrodes by integrating them into a single chip structure. The on-chip metal electrodes provide fast signal modulation, while the integrated reference electrode provides stable potential reference. This combination achieves both high speed and high stability simultaneously.
Solution Approach 2:
The patent implements a feedback control system that uses the sense electrode to monitor the gate voltage and adjusts the drive electrode accordingly. This feedback mechanism compensates for any potential drifts and maintains stable operation while utilizing the fast response of on-chip metal electrodes. The feedback loop ensures both speed and stability are achieved.
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
The system achieves faster and more stable gate voltage modulation, increasing the maximum frequency limit by up to a factor of 5-10, enabling rapid and sensitive detection of substances in bio-sensing applications.
Implementation Method 1
a first sense electrode configured for measuring the voltage at the gate thereby obtaining a first feedback signal indicative of the voltage at the gate
Implementation Method 2
a feedback control system for regulating the voltage at the gate by controlling the first drive electrode using the first feedback signal
Data Source
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AI summary
The present invention relates to a gate driver system (100) for driving a gate (112) of a field-effect transistor (110) in contact with a liquid. The system (100) includes the field-effect transistor with a gate (112), source (111), and drain (113) for biasing. It features a first drive electrode (120) for applying a driving signal to achieve a voltage at the gate. A first sense electrode (130) is used for measuring the gate voltage, providing a first feedback signal indicative of this voltage. The first drive electrode and/or the second drive electrode is an on-chip metal electrode. A feedback control system (140) is incorporated to regulate the gate voltage by controlling the first drive electrode using the first feedback signal. This system (100) is designed to ensure precise control of the gate voltage.