Patent ID: 9684811
Date: 2017-06-20
CPC Classifications: G06K

Claim:
1. A suspended capacitive fingerprint sensor comprising: a substrate; a plurality of capacitive sensing units on the substrate, wherein each of the capacitive sensing units comprises a fixed electrode, a suspended electrode, and a chamber between the fixed electrode and the suspended electrode; and at least one insulation protection layer covering the capacitive sensing units, so that the capacitive sensing units sense a fingerprint of a finger above the insulation protection layer, wherein the suspended electrode and a ridge or a valley of the finger form a sensing capacitance Cfinger, the fixed electrode and the suspended electrode form a reference capacitance Cref, and the suspended electrode and one or more conductive material below the suspended electrode from a parasitic capacitance Cp; and a plurality of operational amplifiers formed on the substrate, wherein the operational amplifiers are electrically connected to the capacitive sensing units, respectively, each of the operational amplifiers has a positive input end, a negative input end, and an output end, the positive input end is electrically connected to a fixed potential, the negative input end is electrically connected to the suspended electrode, an input voltage signal Vin is applied to the finger, and the output end is electrically connected to the fixed electrode and outputs an output voltage Vout, wherein Vout=Vin*(Cfinger/Cref).