The term
solid-state became popular at the beginning of the semiconductor era in the 1960s to distinguish this new technology. A semiconductor device works by controlling an electric current consisting of
electrons or
holes moving within a solid crystalline piece of
semiconducting material such as
silicon, while the
thermionic vacuum tubes it replaced worked by controlling a current of electrons or
ions in a vacuum within a sealed tube. Although the first solid-state electronic device was the
cat's whisker detector, a crude
semiconductor diode invented around 1904, solid-state electronics started with the invention of the
transistor in 1947. Before that, all electronic equipment used
vacuum tubes, because vacuum tubes were the only
electronic components that could
amplify—an essential capability in all electronics. The transistor, which was invented by
John Bardeen and
Walter Houser Brattain while working under
William Shockley at
Bell Laboratories in 1947, could also amplify, and replaced vacuum tubes. The first transistor hi-fi system was developed by engineers at
GE and demonstrated at the
University of Philadelphia in 1955. In terms of commercial production, The Fisher TR-1 was the first "all transistor"
preamplifier, which became available mid-1956. In 1961, a company named Transis-tronics released a solid-state amplifier, the TEC S-15. The replacement of bulky, fragile, energy-hungry vacuum tubes by transistors in the 1960s and 1970s created a revolution not just in technology but in people's habits, making possible the first truly portable
consumer electronics such as the
transistor radio,
cassette tape player,
walkie-talkie and
quartz watch, as well as the first practical
computers and
mobile phones. Other examples of solid state electronic devices are the
microprocessor chip,
LED lamp,
solar cell,
charge coupled device (CCD) image sensor used in cameras, and
semiconductor laser. Also during the 1960s and 1970s,
television set manufacturers switched from vacuum tubes to semiconductors, and advertised sets as "100% solid state" even though the
cathode-ray tube (CRT) was still a vacuum tube. It meant only the chassis was 100% solid-state, not including the CRT. Early advertisements spelled out this distinction, but later advertisements assumed the audience had already been educated about it and shortened it to just "100% solid state".
LED displays can be said to be truly 100% solid-state. ==See also==