Transistors

A transistor is a semiconductor device which allows one electric current to control the flow of another. There are many different types of transistors, but practically all modern ones are //field effect transistors//, or FETs. FETs have three contacts, the //source//, //drain//, and //gate//.

There are two types of FETs: //p-channel// and //n-channel//. In a p-channel, current is allowed to flow between the source and drain only if there is a second current flowing across the gate. An n-channel is just the opposite: current flows through if there is //no// power on the gate. FETs are the basis of all modern electronic computers and can be used to construct logic gates, memory, and more.

Though some transistors are manufactured as discrete components (each in its own little package) most are printed on integrated circuits.