When was the transistor invented?

Explanation

The transistor is the fundamental building block of modern electronic devices. It is a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals. Julius Edgar Lilienfeld patented a field-effect transistor in 1926 but it was not possible to actually construct a working device at that time. The first practically implemented device was a point-contact transistor invented in 1947 by American physicists John Bardeen, Walter Brattain, and William Shockley.