A differential acquisition and amplification circuit for capacitive fingerprint signals and its working method

Abstract

The present invention proposes a differential acquisition and amplification circuit for capacitive fingerprint signals and its working method. By collecting the DC and AC components on the chip, the common mode can be subtracted from the final signal conveniently before secondary amplification, effectively The common-mode DC component and AC component in the original signal are filtered out, and a very high sensitivity and dynamic range can be obtained, and then the above-mentioned differential-mode signal is amplified by Cs / Ci times; at the same time, in the secondary amplification stage, through the In the layout, the amplification capacitor Cs and the second integration capacitor Ci2 are matched to minimize signal distortion during the secondary amplification process.

Description

technical field [0001] The invention relates to the technical field of integrated circuit design and fingerprint detection, in particular to a common-mode compensation and signal amplification circuit for small fingerprint signals. Background technique [0002] Due to its high reliability and cost-effectiveness, fingerprint authentication has become the mainstream of current biometric authentication; and capacitive fingerprint sensor is characterized by its small size, fast speed, low power consumption, high detection degree and great ease of use. , has become the mainstream method in fingerprint authentication, and has become the focus of current research. [0003] In the design of a capacitive fingerprint sensor, due to ESD and physical protection considerations, the thickness of the insulating medium on the fingerprint sensor is usually greater than 50 μm. The increase in the thickness of the insulating medium makes the effective fingerprint signal that can be collected ...

AI Technical Summary

Problems solved by technology

The increase in the thickness of the insulating medium makes the effective fingerprint signal that can be collected become very small. On the one hand, it is easily overwhelmed by various DC signals on the chip, such as static leakage current, parasitic, etc.; This has become a major difficulty in the current design of capacitive fingerprint sensors. If this problem cannot be effectively solved, the signal sensitivity and dynamic range required to push the product to stable mass production cannot be obtained.

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