Semiconductor Diode – 1874 A.D.

Return to Timeline of the History of Computers


Semiconductor Diode

Michael Faraday (1791–1867), Karl Ferdinand Braun (1850–1918)

“Semiconductors are curious devices: not quite conductors like copper, gold, or silver, not quite insulators like plastic or rubber. In 1833, Michael Faraday discovered that the chemical silver sulfide became a better conductor when heated, unlike metals that lose their conductivity under the same conditions. Separately, in 1874, Karl Ferdinand Braun, a 24-year-old German physicist, discovered that a metal sulfide crystal touched with a metal probe would conduct electricity in only one direction. This “one direction” characteristic is what defines diodes or rectifiers, the simplest electronic components.”

“In 1904 the British chemist John-Ambrose Fleming had invented the two-element amplifier, or ‘diode’, and a few months before DeForest the Austrian physicist Robert von Lieben had already built a three-element amplifier, or triode.” (Fair Use: B07XVF5RSP)

“Braun’s discovery was a curiosity until the invention of radio. The diode proved critical in allowing radio to make the transition from wireless telegraphy to the transmission and reception of the human voice. The diode of choice for these early radio sets was frequently called a cat’s whisker diode, because it consisted of a crystal of galena, a form of lead sulfide, in contact with a spring of metal (the “whisker”). By carefully manipulating the pressure and orientation of the metal against the crystal, an operator could adjust the electrical properties of the semiconductor until they were optimal for radio reception. Powered only by the radio waves themselves, a crystal set was only strong enough to faintly produce sounds in an earphone.”

“Crystal radio receivers were used onboard ships and then in homes until they were replaced by new receivers based on vacuum tubes, which could amplify the faint radio waves so that they were strong enough to power a speaker and fill a room with speech or music. But tubes didn’t mark the end of the crystal radio: the devices remained popular for people who couldn’t get tubes—such as on the front lines in World War II — as well as among children learning about electronics. In the 1940s, scientists at Bell Labs turned their attention to semiconductor radios once again in an effort to perfect microwave communications. In the process, they discovered the transistor.”

“Braun went on to make other fundamental contributions to physics and electronics. In 1897, he invented the cathode-ray tube (CRT), which would become the basis of television. He shared the 1909 Nobel Prize with Guglielmo Marconi (1874–1937) “in recognition of their contributions to the development of wireless telegraphy.””

SEE ALSO: Silicon Transistor (1947)

Crystal Detector, made by the Philmore Manufacturing Company. To use this device, the operator would connect a wire to each of the two flanges and press the metal “whisker” into the semiconductor crystal.”

Fair Use Sources:

Main: B07C2NQSPV

Secondary: B07XVF5RSP