Patent ID: 9152841
Filing Date: 2015-10-06
Classification: A61B,G01R,G06K,G07C

Abstract:
1. A capacitive fingerprint sensing device for sensing a fingerprint pattern of a finger, said fingerprint sensing device comprising a semiconductor substrate; and an array of sensing elements formed on said semiconductor substrate, wherein each of said sensing elements comprises: a protective dielectric top layer to be touched by said finger; an electrically conductive sensing structure arranged underneath said top layer; and a charge amplifier connected to said sensing structure for providing a sensing signal indicative of a change of a charge carried by said sensing structure resulting from a change in a potential difference between said finger and said sensing structure, said charge amplifier comprising: wherein said sense transistor is formed in a well in said semiconductor substrate, an interface between said well and said substrate being configured in such a way that current can be prevented from flowing between said well and said substrate; and wherein said charge amplifier is configured in such a way that a potential at said negative input substantially follows a potential at said positive input, wherein said fingerprint sensing device further comprises: excitation signal providing circuitry, said excitation signal providing circuitry being: