Bernard D. H. Tellegen

Bernard D. H. Tellegen (1900 to 1990) was a Dutch electrical engineer and inventor of the pentode and the gyrator, also known for a theorem in circuit theory that bears his name. He obtained a master's degree in electrical engineering from Delft University in 1923 and joined the Philips Natuurkundig Laboratorium, the Philips Physics Laboratory in Eindhoven. In 1926, together with Gilles Holst, he invented the pentode vacuum tube. Around 1948 he invented the gyrator, a circuit element that can simulate the effect of an inductor without a coil and is used, for example, in hi-fi graphic equalizers. He held 41 US patents. From 1946 to 1966 he was an adjunct professor of circuit theory at the University of Delft, and from 1942 to 1952 he was president of the Netherlands Electronics and Radio Society. He was a Fellow of the IEEE and won its Edison Medal in 1973, and he was elected a member of the Royal Netherlands Academy of Arts and Sciences in 1960.