Harold Black and the negative-feedback amplifier

On August 2, 1927, Harold Black, a young Bell Labs engineer just six years out of college, invented the negative-feedback amplifier. Negative feedback soon allowed the Bell system to reduce overcrowding of lines and extend its long-distance network by means of carrier telephony. It enabled the design of accurate fire-control systems in World War II, and it formed the basis of early operational amplifiers, as well as precise, variable-frequency audio oscillators. The invention, its development, the role it played in the founding of the Hewlett-Packard company, and the themes it illustrates in the history of technology are discussed.<
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