Main Page | See live article | Alphabetical index

John Ambrose Fleming

Sir John Ambrose Fleming (sometimes also listed as Ambrose J. Fleming, November 29, 1848 - April 18, 1945) was a British electrical engineer.

Early years

Fleming was born in Lancaster and educated at University College School, London and UCL. Lecturer at a number of universities including Cambridge, Nottingham and UCL. Consultant to the Marconi Wireless Telegraph Company, Swan, Ferranti, Edison Telephone and later the Edison Electric Light Company.

In 1892 Fleming presented an important paper on transformer theory to the Institution of Electrical Engineers in London.

Later years

In November 1904 he invented and patented the two-electrode radio rectifier, which he called the oscillation valve. It was also called a thermionic valve, vacuum diode, kenotron, thermionic tube, or Fleming valve. This invention is often considered to have been the beginning of electronics.

In 1906 Lee De Forest of the USA added a control grid to the valve to create a vacuum tube RF detector called the Audion, leading Fleming to accuse him of plagiarism. De Forest's device was later refined into an amplifier.

Fleming contributed in the fields of photometry, electronics, wireless telegraphy and electrical measurements. He was knighted in 1929 and died at Sidmouth in Devon.