Sensor Used in E-nose - The Electronic Nose Artificial Olfaction Technology - page 163

Fig. 6.17 Representation of

FET

time-dependent signal can be monitored and the response is easy to calculate.
Basic structure representation of FET is shown in Fig. 6.17 .
The source-drain conductivity of the FET can be modulated by adjusting the
strength of electrical field between the gate electrode and the silicon, or through
the presence of absorbed species and the resulting polarization phenomena. In FET,
the influence of sample gases change the value of the transistor threshold voltage.

6.8 Metal Oxide Semiconductor Field Effect Transistor

The Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is the leading
device used and has taken the limelight compare to the other technologies for a
number of reasons, though mainly due to its simple structure. It is a transducer
device used in E-nose to transform a physical/chemical change into an electrical
signal. It is basically a four-terminal device (as shown in Fig. 6.18 ) in which
current flow is controlled by an externally applied vertical electric field. When

Fig. 6.18 MOSFET schematic