Karl Ferdinand Braun (6 June 1850 – 20 April 1918) was a German inventor, physicist and Nobel laureate in physics. Braun contributed significantly to the development of the radio and TV technology: he shared with Guglielmo Marconi the 1909 Nobel Prize in Physics.
Braun was born in Fulda, Germany, and educated at the University of Marburg and received a Ph.D. from the University of Berlin in 1872. In 1874 he discovered that a point-contact semiconductor rectifies alternating current. He became director of the Physical Institute and professor of physics at the University of Strassburg in 1895.
In 1897 he built the first cathode-ray tube(CRT) and cathode ray tube oscilloscope. CRT technology is only now in the 2000s, over a century later, gradually being replaced by flat screen technologies (such as liquid crystal display(LCD), light emitting diode(LED) and plasma displays) on television sets and computer monitors. The CRT is still called the "Braun tube" in German-speaking countries (Braunsche Röhre) and in Japan (Buraun-kan).
During the development of radio, he also worked on wireless telegraphy. In 1897 Ferdinand Braun joined the line of wireless pioneers. His major contributions were the introduction of a closed tuned circuit in the generating part of the transmitter, and its separation from the radiating part (the antenna) by means of inductive coupling, and later on the usage of crystals for receiving purposes. Wireless telegraphy claimed Dr. Braun's full attention in 1898, and for many years after that he applied himself almost exclusively to the task of solving its problems. Dr. Braun had written extensively on wireless subjects and was well known through his many contributions to the Electrician and other scientific journals. In 1899, he would apply for the patents, Electro telegraphy by means of condensers and induction colls and Wireless electro transmission of signals over surfaces.
Around 1898, he invented a crystal diode rectifier or Cat's whisker diode. Pioneers working on wireless devices eventually came to a limit of distance they could cover. Connecting the antenna directly to the spark gap produced only a heavily damped pulse train. There were only a few cycles before oscillations ceased. Braun's circuit afforded a much longer sustained oscillation because the energy encountered less losses swinging between coil and Leyden Jars. And by means of inductive antenna coupling the radiator was better matched to the generator. The resultant stronger and less bandwidth consuming signals bridged a much longer distance.
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