Patent ID: 7688082

Claim:
A capacitive fingerprint sensor, comprising: a first transistor having a gate terminal, an input terminal and an output terminal, wherein the gate terminal is controlled by a first readout select line, and the input terminal is connected to a first bias voltage VA; a fingerprint capacitor connected to the output terminal of the first transistor, wherein the fingerprint capacitor has a capacitance that is either a valley capacitance C FV or a ridge capacitance C FR , and C FV is smaller than C FR ; a second transistor having a gate terminal, an input terminal and an output terminal, wherein the gate terminal is controlled by a second readout select line, the input terminal is connected to a second bias voltage VB, the output terminal is connected to the fingerprint capacitor, and the second readout select line is immediately next to the first readout select line; and a third transistor having a gate terminal, an input terminal and an output terminal, wherein the gate terminal is controlled by a scan line, the input terminal is connected to the fingerprint capacitor, and the output terminal is connected to a readout line.