Amplifier by their physical placement in the signal chain; a preamplifier may precede other signal processing stages, for example. The first practical electrical device which could amplify was the triode vacuum tube, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912. Today most amplifiers use transistors. The first practical device that could amplify was the triode vacuum tube, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912. Vacuum tubes were used in almost all amplifiers until the 1960s–1970s when the transistor, invented in 1947, replaced them. Today, most amplifiers
Charles Brown (engineer) Charles Brown (engineer) Charles Brown (1827–1905) was a British engineer. He was born at Uxbridge on 30 June 1827 and was apprenticed to Maudslay, Sons and Field. In 1851 he moved to Switzerland to join the Sulzer company. In 1871 he left Sulzer to set up Swiss Locomotive and Machine Works (SLM). While at SLM he invented the Brown valve gear, a radial valve gear for steam engines. He became involved in the development of electric locomotives in the 1880s. In 1885 he became manager of Maschinenfabrik Oerlikon and in 1890 he set up Charles Brown and Company at 91