For each pixel in an array of pixels in a fingerprint sensor, a fingerprint capacitor
is defined by the fingerprint-bearing skin of a user's finger proximate to the
top exposed surface of a sensing plate of the pixel. First and second plates are
embedded in dielectric material beneath the sensing plate, and define therewith
first and second capacitors of a sensing element. The capacitance of the fingerprint
capacitor is coupled by the sensing element to an amplifier. During a sensing operation,
the amplifier generates a pixel output signal that is a function of the variable
capacitance of the fingerprint capacitor, which varies according to the presence
of a fingerprint ridge or valley appearing directly above the sensing plate when
the user's finger is in contact with the fingerprint sensor.
