Fingerprint Sensor Transistor Circuit for Recognition Accuracy
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Solution Overview
Problem
Current fingerprint sensors in display devices face challenges in achieving optimal sensitivity due to threshold voltage characteristics of transistors, which affect the accuracy of fingerprint recognition.
Innovation Solution
The implementation of a fingerprint sensor design that includes a photodetector and multiple transistors (first, second, third, and fourth) to manage voltage and reset signals, allowing for improved connection and reset mechanisms to enhance sensitivity by compensating for transistor threshold voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional fingerprint sensor design is used, then the device structure is simple, but the sensitivity and fingerprint recognition accuracy are insufficient due to threshold voltage characteristics of transistors
Solution Approach 1:
The sensor pixel is divided into multiple functional components: photodetector, first transistor, second transistor, third transistor, and fourth transistor. Each component has a specific function in the sensing and signal processing chain, allowing the system to achieve higher measurement precision through specialized sub-components while managing overall complexity through functional segmentation.
Solution Approach 2:
The multiple transistors in the sensor pixel serve multiple functions: signal amplification, reset operations, and threshold voltage compensation. This multi-functionality allows a single integrated pixel structure to achieve both high sensitivity and accurate fingerprint recognition without requiring separate dedicated components for each function.
2Reliability
If threshold voltage compensation mechanisms are implemented, then sensitivity is improved, but the transistor circuit complexity increases
Solution Approach 1:
The third transistor applies a reset voltage to the first node before the photodetector integration period begins, and the fourth transistor connects the first node to the second node to initialize the signal path. This preliminary resetting action ensures that threshold voltage variations are compensated for before signal acquisition, improving sensitivity while using a straightforward two-transistor reset mechanism rather than complex continuous compensation circuits.
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 design significantly improves the sensitivity of fingerprint sensors by distinguishing between ridges and valleys of a fingerprint, leading to enhanced fingerprint recognition accuracy.
Implementation Method 1
a photodetector; a first transistor configured to connect a second node with a third node based on a voltage of a first node, the first node corresponding to a first electrode of the photodetector
Data Source
AI summary
A fingerprint sensor includes four transistors and a photodetector. The first transistor connects a second node with a third node based on a voltage of a first node, where the first node corresponding to a first electrode of the photodetector. The second transistor connects the second node with a read-out line based on a scan signal. The third transistor supplies a reset voltage to the first node based on a first reset signal. The fourth transistor connects the first node with the second node based on a second reset signal.