A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power.

It is composed of semiconductor material with at least three terminals for connection to an external circuit. The transistor is the fundamental building block of modern electronic devices. Following its development in 1947 by American physicists John Bardeen, Walter Brattain, and William Shockley, the transistor revolutionized the field of electronics and paved the way for smaller and cheaper radios, calculators, and computers, among other things. The inventors were jointly awarded the 1956 Nobel Prize in Physics for their achievement.

Boy’s transistor radio

This is a miniature transistor radio, with the words '1-transistor' on the front and 'boy's radio' on the reverse. It was made in Japan, probably in the 1960s, for the export market. US tariffs on Japanese radios were higher than for Japanese toys. US tariff law did not define a radio containing two transistors or less as a radio but instead classified it as a toy. Japan took advantage of this legislation to produce many different radios containing two transistors or less. Most were not aimed at children.