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
Owen Williams (engineer) excelled in mathematics. He was apprenticed to the Electrical Tramways Co. in London in 1907 and at the same time did an engineering degree at the University of London. In 1912 Williams assumed a position as engineer and designer with the Trussed Concrete Company. Seven years later, he started his own consulting firm, Williams Concrete Structures. He was then appointed chief consulting civil engineer to the British Empire Exhibition which included the old Wembley Stadium. The commission also included the Palace of Industry building in Brent, the first building in the United Kingdom to use concrete as the exterior. The