Duodiode

First working transistor

At the same time some European scientists were led by the idea of solid-state amplifiers. The German physicist Herbert F. Mataré (1912–2011) had conducted experiments at Telefunken with what he called "Duodiode" (double diode) from 1942, when he first observed transconductance effects with silicon diodes manufactured for German radar equipment for WWII. Finally on August 13, 1948, Mataré and Heinrich Welker (1912–1981), working at Compagnie des Freins et Signaux Westinghouse in Aulnay-sous-Bois, France applied for a patent on an amplifier based on the minority carrier injection process which they called the "Transistron". The device was shown publicly on May 18, 1949. Transistrons were commercially manufactured for the French telephone company and military, and in 1953 a solid-state radio receiver with four transistrons was demonstrated at the Düsseldorf Radio Fair.