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
John Snell (electrical engineer) Central Electricity Board was established, the national grid created and the supply of electricity standardised. He was made GBE in 1925. In 1928 he began introducing major new electricity power systems in the West of England with his friend and then colleague, Dr John A. Purves. He was awarded the Faraday Medal for 1938 by the Institution of Electrical Engineers (now the Institution of Engineering and Technology). He died after an operation at the London Clinic in 1938. He had married Annie Glendenning Quick of Biscovey, Cornwall, with whom he had at least one son. John Snell (electrical engineer) Sir