Basic electronic principles

'Electronics' usually refers to devices where electricity is conducted through a vacuum, gas, or semiconductors.

Automotive applications mostly use semiconductors such as diodes, transistors, and power transistors. Their electrical resistance is higher than that of most conductors, but lower than that of most insulators.

A semiconductor's conducting ability depends on two kinds of charge carriers:

• The first is familiar - the negative electron. This kind of semiconductor contains an excess of free electrons. They can be made to flow, and carry charge.
• The second type of charge carrier occurs from a loss of electrons - with gaps, called holes, where the electrons were. Since negative electrons have been lost, they are called positive holes. And because they are positive, a voltage can make them move, towards the negative pole.

The number of charge carriers in a material can be altered by doping, or adding very small quantities of impurities. A doped semiconductor always has an excess of one type of charge carrier. Electrons in excess make it an n-type semiconductor. N for negative. Holes in excess make it p-type. P for positive.

When connected into a circuit, both the electrons and the holes move and current can be thought of as moving in two directions. So electron current and conventional current are both used in electronics.