A biometric system requires a users personal attributes for
identity such as iris, fingerprints etc. fingerprint biometrics are one of the simplest,
cheapest and common forms of security in terms of biometrics today. Capacitive
scanners are used on various mobile phones these days. The scanner simply
creates a picture of ridges engraved on an individuals skin in order to gain
authorisation. Optical scanners are another type of fingerprint biometric which
use light to determine authorisation, however capacitive scanners use
electrical currents. Sensors are made through various conductor chips that hold
an array of small cells. Each individual cell has two conductor plates which
are covered with insulating layers and the sensor is supported by an electrical
circuit, designed around an operational amplifier. The amplifier is made up of
three elements which are: capacitors, resistors and transistors. Similar to an
amplifier, an reversing amplifier changes one current simply due to variations
in a different current. The reversing amplifier then changes a voltage. This change
is  established on the voltage of an
reversing terminal and a non-reversing terminal. The reversing terminal is
joined to a reference voltage supply and something called a feedback loop, this
specific loop includes two conductor plates. In order to scan a fingerprint the
processor shuts down the reset switch on every individual cell and the outcome
of this is that it shortens the amplifier input and output in order to stabilise
the integrator circuit. When the switch opens again the processor enables a set
charge to the circuit and this further leads to the capacitors charging up. The
scanner records the voltage output and decides if it actually matches the
appearance of a ridges and valley’s of the person. After recording the cells in
the sensor array, the processor then creates a photo of the fingerprint which
is comparable by an optical scanner.