Dual-Gate ISFET Pixel Circuit In-Pixel Amplification
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Solution Overview
Problem
Current ion-sensitive field effect transistor (ISFET) arrays face limitations in sensitivity and measurement range, with signal amplification often occurring outside the pixel, which can amplify noise and reduce measurement accuracy.
Innovation Solution
A dual-gate ion-sensitive transistor pixel circuit with a feedback connection between the second gate and drain, allowing for signal amplification between the first and second gates, and a readout device connected to the second gate, enhancing sensitivity and reducing noise influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal amplification is performed outside the pixel circuit, then measurement range is extended, but noise is also amplified and measurement accuracy deteriorates
Solution Approach 1:
The patent divides the amplification function into two segments: in-pixel amplification (first amplification stage) and post-pixel amplification (second amplification stage). The in-pixel amplifier provides initial signal boosting while the feedback transistor suppresses noise, achieving a balance between signal amplification and noise reduction that resolves the contradiction between measurement accuracy and noise amplification.
Solution Approach 2:
The patent introduces a feedback transistor that provides negative feedback from the output node to the gate of the first transistor in the in-pixel amplifier. This feedback mechanism stabilizes the operating point, reduces noise, and improves linearity, thereby enhancing measurement accuracy while preventing excessive noise amplification.
2Measurement precision
If in-pixel amplification is implemented, then sensitivity is improved, but pixel circuit complexity increases
Solution Approach 1:
The patent merges the amplification function with the existing pixel circuit structures by integrating the in-pixel amplifier and feedback transistor into the ISFET readout circuitry. This consolidation achieves sensitivity improvement without proportionally increasing complexity, as the amplification is embedded within the existing pixel architecture rather than added as a separate external component.
3Measurement precision
If dual-gate transistor structure is used for amplification, then sensitivity to pH changes increases, but manufacturing complexity increases
Solution Approach 1:
The dual-gate transistor structure serves multiple functions: the first gate receives the pH-sensitive signal, the second gate provides control for amplification, and the transistor itself acts as both the sensing element and the amplifying element. This multi-functionality achieves high sensitivity to pH changes while minimizing manufacturing complexity by eliminating the need for separate sensing and amplification components.
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 configuration increases sensitivity to pH changes and biomolecule detection, improves measurement accuracy, and expands chemical and biochemical sensing applications by amplifying signals within the pixel circuit, reducing noise and enabling higher sensor density and multiplexed detection.
Implementation Method 1
A dual-gate ion-sensitive transistor pixel circuit with a feedback connection between the second gate and drain, allowing for signal amplification between the first and second gates
Data Source
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AI summary
A pixel circuit acts as a sensing element in a sensing device. The pixel circuit includes a sensing electrode, a first gate electrically connected to the sensing electrode, a second gate in electrical communication with the first gate, and a readout device that is electrically connected to the second gate. An input voltage applied to the sensing electrode is amplified between the first gate and the second gate, the amplification being measured as an output signal from the readout device to perform a sensing operation. For example, the output signal may be relatable to pH, analyte measurements, or other properties of sample liquids analyzed by the sensing device. A sensing device may include multiple pixels disposed on a substrate, each pixel including said pixel circuit. Driver circuits controlled by control electronics are configured to generate signals that selectively address the pixels and to read out voltages at the sensing electrodes.