Fingerprint Driving Circuit Two-Stage Amplification
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Solution Overview
Problem
Conventional fingerprint driving circuits face challenges in distinguishing the small voltage difference between fingerprint valleys and ridges, leading to difficulties in signal readout due to weak photoresponse and noise interference, which results in low readout accuracy.
Innovation Solution
A two-stage amplifying circuit is introduced, with a common-drain structure for voltage amplification and a common-source structure for current and power amplification, enhancing the voltage difference and output ability of the fingerprint signal, allowing for accurate signal readout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional single-stage amplifying circuit is used, then the circuit structure is simple, but the voltage difference between fingerprint valley and ridge signals cannot be effectively amplified
Solution Approach 1:
The patent divides the amplifying circuit into two stages: a first amplifying unit for voltage amplification and a second amplifying unit for current and power amplification. This segmentation allows each stage to perform a specific function, achieving effective voltage difference amplification while maintaining reasonable circuit complexity through modular design.
2Measurement precision
If the fingerprint signal is directly read out without amplification, then the readout process is fast, but the small voltage difference between valley and ridge signals is lost due to weak photoresponse and noise interference
Solution Approach 1:
The patent applies preliminary amplification action to the fingerprint signal before readout. The first amplifying unit performs voltage amplification on the weak fingerprint signal in advance, and the second amplifying unit performs current and power amplification, ensuring the signal is sufficiently strengthened before transmission to the IC, thereby preventing signal loss due to weak photoresponse and noise interference.
3Power
If a larger RC loading is used in the circuit, then the driving ability is enhanced, but the small fingerprint signals are further attenuated and lost
Solution Approach 1:
The patent introduces an intermediary amplifying circuit between the fingerprint sensor and the readout IC. The first amplifying unit acts as an intermediary to buffer and amplify the weak signal, and the second amplifying unit further strengthens it, allowing the signal to withstand larger RC loading without being attenuated or lost during transmission.
4Measurement precision
If noise filtering is applied to distinguish valley and ridge signals, then the readout accuracy improves, but the circuit complexity and processing time increase
Solution Approach 1:
The patent changes the amplitude parameter of the fingerprint signal through two-stage amplification. By significantly increasing the voltage difference between valley and ridge signals through the first and second amplifying units, the signals become easily distinguishable without requiring complex noise filtering circuits or extended processing time.
Data Source
AI summary
A fingerprint driving circuit and a display panel are provided. A first stage of amplifying unit is configured to receive a fingerprint voltage, perform a voltage amplifying process on the fingerprint voltage, and output the fingerprint voltage on which the voltage amplifying process has been performed. A second stage of amplifying unit is configured to receive the fingerprint voltage on which the voltage amplifying process has been performed, perform a current and power amplifying process on the fingerprint voltage on which the voltage amplifying process has been performed, and output the fingerprint voltage on which the current and power amplifying process has been performed. A voltage difference between a valley and a ridge of a fingerprint is amplified, so that the signal can be read out easily and correctly and the output ability of the signal is enhanced.