Capacitive fingerprint sensing device with current readout from sensing elements
Abstract:
The present invention relates to a capacitive fingerprint sensing device comprising a plurality of sensing elements. Each sensing element includes a protective dielectric top layer to be touched by a finger; an electrically conductive sensing structure arranged underneath the top layer; a charge amplifier connected to the sensing structure for providing a sensing voltage signal indicative of a change of a charge carried by the sensing structure resulting from a change in a potential difference between the finger and the sensing structure; and a voltage-to-current converter for converting the sensing voltage signal to a sensing current signal indicative of the change of charge carried by the sensing structure. Hereby, accurate sensing as well as faster operation of the sensing elements can be achieved without a corresponding increase in power consumption.
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