  harold stephen black (april 14, 1898 â december 11, 1983) was an american electrical engineer, who revolutionized the field of applied electronics by inventing the negative feedback amplifier in 1927. to some, his invention is considered the most important breakthrough of the twentieth century in the field of electronics, since it has a wide area of application. this is because all electronic devices (vacuum tubes, bipolar transistors and mos transistors) are inherently nonlinear, but they can be made substantially linear with the application of negative feedback. negative feedback works by sacrificing gain for higher linearity (or in other words, smaller distortion or smaller intermodulation). by sacrificing gain, it also has an additional effect of increasing the bandwidth of the amplifier. however, a negative feedback amplifier can be unstable such that it may oscillate. once the stability problem is solved, the negative feedback amplifier is extremely useful in the field of electronics. black published a famous paper, stabilized feedback amplifiers, in 1934. == biography == he was born in leominster, massachusetts in 1898. he went to worcester polytechnic institute (wpi) for his first degree. subsequently, he received a b.s.s. in electrical engineering from wpi in 1921 and then joined western electric, which was the manufacturing arm of at&t. he joined bell labs (1925), where he was a member of technical staff until his retirement (1963). black started writing his autobiography with the tentative title "before the ferry docked". however, he died in december 1983 at age 85 before he could finish it. == work == amplifiers are unavoidably non-linear. therefore, every time a signal is amplified in a telecommunications network, which can happen dozens of times in a circuit, noise and distortion are added. black first invented the feed-forward amplifier which compares the input and output signals and then negatively amplifies the distortion and combines the two signals, canceling out some of the distortion. this amplifier design improved, but did not solve, the problems of transcontinental telecommunication.harold black and the negative-feedback amplifier, ronald kline, ieee control systems, aug 1993, volume 13, issue 4, pages 82-85 afte
1898_births 1983_deaths American_electrical_engineers American_inventors Control_theorists Cyberneticists People_from_Leominster,_Massachusetts Scientists_at_Bell_Labs Worcester_Polytechnic_Institute_alumni