
highly versatile operational amplifiers popularly
known as op amps.
Op amps have a very long history. Several
engineers experimented with vacuum tube
feedback amplifiers in the 1920s, and Bell Labs
scientist Harold S. Black applied for a patent on
the method. The patent office was not convinced
the method would work, so they sat on Black’s
application for nearly a decade. Finally, in 1932
Black received US Patent US2102671 for his
invention. Back then, op amps were made with
vacuum tubes and were eventually used in
analog computers for both military and scientific
applications.
Op amps have inverting (–) and non-inverting
(+) inputs (Figur