SEMICONDUCTOR MATERIALSCreated and Presented by Doren Nedrick

The Basic Principles Of Heat Sensitive DevicesA change in temperature results in a change in its resistance depending on the temperature coefficient. For a device with a negative temperature coefficient (most common), its resistance decreases as the temperature increases as shown by the resistance-temperature graph in fig. 1

ThermistorThermistors also called thermal resistors are semiconductor devices whose use as transducers is due to the fact that their resistance changes when their temperature increases. There are three types namely: the rod-shaped, disc-shaped and the bead shaped and its symbol is

Thermistors are used for the measurement and control of temperature, being heated either externally or internally by the current they carry.Used as a means of sensing temperature change. Commonly found embedded in motor windings to detect overheating.

ThermocoupleThermocouple is a thermoelectric device for measuring or sensing temperature difference, consisting of two wires of dissimilar metals connected at two points, between which a voltage is developed in proportion to any temperature difference. Its application therefore is to measure temperatures accurately

SemiconductorsAn insulator is any material that opposes the flow of electrons (current).A conductor is any material which allows for free flow of electrons (current). Semi means half. A semiconductor therefore is a material that has a conductivity level somewhere between the extremes of an insulator and a conductor.

An atom is made up tiny particles. Two of these particles, the electron and the proton are important to our studies. Electrons move around the center, or nucleus, of an atom in paths. These paths are usually called shells

An atom can have several shells around the nucleus. Each of these shells can have only up to a certain number of electrons. The number is called the quota of the shell. The first shell can hold two electrons while the second, third, fourth and so on can hold eight. When every shell of an atom contains its quota of electrons, the atom is said to be in stable condition.

The proton carries a positive charge while the electron carries negative. Recall a material with a lot of electrons free to move are called conductors and a material that have a shortage is called an insulator. For semiconductor it is somewhere between that (having just about half its quota) eg silicon and germanium - having four (4) valence electrons,

Crystal Lattice of SiliconThe resistance of a semiconductor decreases with temperature rise

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