Black, Harold Stephen

SUBJECT AREA: Electronics and information technology, Recording, Telecommunications

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b. 14 April 1898 Leominster, Massachusetts, USA

d. 11 December 1983 Summitt, New Jersey, USA

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American electrical engineer who discovered that the application of negative feedback to amplifiers improved their stability and reduced distortion.

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Black graduated from Worcester Polytechnic Institute, Massachusetts, in 1921 and joined the Western Electric Company laboratories (later the Bell Telephone Laboratories) in New York City. There he worked on a variety of electronic-communication problems. His major contribution was the discovery in 1927 that the application of negative feedback to an amplifier, whereby a fraction of the output signal is fed back to the input in the opposite phase, not only increases the stability of the amplifier but also has the effect of reducing the magnitude of any distortion introduced by it. This discovery has found wide application in the design of audio hi-fi amplifiers and various control systems, and has also given valuable insight into the way in which many animal control functions operate.

During the Second World War he developed a form of pulse code modulation (PCM) to provide a practicable, secure telephony system for the US Army Signal Corps. From 1963–6, after his retirement from the Bell Labs, he was Principal Research Scientist with General Precision Inc., Little Falls, New Jersey, following which he became an independent consultant in communications. At the time of his death he held over 300 patents.

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Principal Honours and Distinctions

Institute of Electronic and Radio Engineers Lamme Medal 1957.

Bibliography

1934, "Stabilised feedback amplifiers", Electrical Engineering 53:114 (describes the principles of negative feedback).

21 December 1937, US patent no. 2,106,671 (for his negative feedback discovery.

1947, with J.O.Edson, "Pulse code modulation", Transactions of the American Institute of Electrical Engineers 66:895.

1946, "A multichannel microwave radio relay system", Transactions of the American Institute of Electrical Engineers 65:798.

1953, Modulation Theory, New York: D.van Nostrand.

1988, Laboratory Management: Principles \& Practice, New York: Van Nostrand Rheinhold.

Further Reading

For early biographical details see "Harold S. Black, 1957 Lamme Medalist", Electrical Engineering (1958) 77:720; "H.S.Black", Institute of Electrical and Electronics Engineers Spectrum (1977) 54.

See also: Bode, Hendrik Wade; Nyquist, Harry

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