Importance:

The transistor is the main active component in practically all current electronics, and is considered through many to be one of the greatest inventions of the 20^th century. Its significance in today's society rests on its capability to be mass produced by using a highly automated process (semiconductor device fabrication) that acquires astonishingly low per-transistor costs.

Even though various companies each produce over a billion individually packaged (termed as discrete) transistors every year, the great majority of transistors now produced are in integrated circuits (frequently shortened to IC, microchips or simply chips), together with diodes, resistors, capacitors and another electronic components, to generate complete electronic circuits. A logic gate contains up to about twenty transistors while an advanced microprocessor, as of 2009, can make use of as much as 2.3 billion transistors that are MOSFETs. "Approximate 60 million transistors were built this year [2002] ... for [each] man, woman, and child in this universe."

The low cost, flexibility, and reliability of transistor have made it a ubiquitous device. Transistorized mechatronic circuits have changed electromechanical devices in controlling appliances and machinery. It is frequently easier and cheaper to make use of a standard microcontroller and write a computer program to perform a control function than to design an equivalent mechanical control function.