Apparatus and Method for TFT Fingerprint Sensor

A fingerprint sensor, comprising:

• a first substrate having a plurality of pixels formed therein, the pixels being arranged in a pixel array of R rows and N columns, each pixel comprising a switching device and a capacitive plate;
• a plurality of R row addressing electrodes, each such row addressing electrode being coupled to the switching devices of the pixels in a corresponding row of the pixel array for selectively enabling the switching devices in the corresponding pixel row;
• a plurality of N data electrodes, each such data electrode being coupled to the switching devices of the pixels in a corresponding column of the pixel array for sensing a signal provided by the capacitive plate of the pixel located at an intersection of a selected pixel row and the corresponding column of the pixel array;
• a cover layer overlying the first substrate for receiving a fingertip of a user;
• and
• a plurality of differential amplifiers, each differential amplifier having a first input coupled to a corresponding one of the plurality of data electrodes and having a second input coupled to a selected one of the plurality of data electrodes serving as a reference electrode, each differential amplifier having an output terminal for providing an output signal, the output signal provided by each differential amplifier being representative of the difference between the data signal provided by its corresponding data electrode and a signal provided by the reference electrode.