A transistor is a three-terminal semiconductor device that can be used for amplification, switching, voltage stabilization, signal modulation,oscillator and many other functions. The transistor is the fundamental building block of both digital and analog integrated circuits — the circuitry that governs the operation of computers, cellular phones, and all other modern electronics.
The transistor is considered by many to be one of the greatest inventions in modern history, ranking in importance with the printing press, automobile and telephone. It is the key active component in practically all modern electronics. Its importance in today's society rests on its ability to be mass produced using a highly automated process (fabrication) that achieves vanishingly low per-transistor costs.