Valve amplifier thermionic valves. The simplest valve was invented by John Ambrose Fleming while working for the Marconi Company in London in 1904 and named the diode, as it had two electrodes. The diode conducted electricity in one direction only and was used as a radio detector and a rectifier. In 1906 Lee De Forest added a third electrode and invented the first electronic amplifying device, the triode, which he named the "Audion". This additional "control grid" modulates the current that flows between cathode and anode. The relationship between current flow and plate and grid voltage is often represented as a series
David Davies (electrical engineer) David Davies (electrical engineer) Sir David Evan Naunton Davies , known as Den Davies or David "DEN" Davies, (born 1935) is a British electrical engineer and educator. He was knighted for services to science in 1994. 1985-1988: Head of the Department of Electronic and Electrical Engineering at University College London (UCL), and holder of the Pender Chair, having already been lecturing there, in "Communications Systems", for many years prior to that. 1986-1988: Vice-Provost of University College London 1988-1993: Vice Chancellor of Loughborough University 1993–1999: Chief Scientific Adviser for the Ministry of Defence 1994-1995: President of the Institution of Electrical Engineers