Operational amplifier

An operational amplifier is a high-gain direct-coupled amplifier that is normally used in feedback connections. If the amplifier characteristics are satisfactory, the transfer function of the amplifier with feedback can often be controlled primarily by the stable and well-known values of passive feedback elements.
The term operational amplifier evolved from original applications in analog computation where these circuits were used to perform various mathematical operations such as summation and integration. Because of the performance and economic advantages of available units, present applications extend far beyond the original ones, and modern operational amplifiers are used as general purpose analog data-processing elements. High-quality operational amplifiers were available in the early 1950s. These amplifiers were generally committed to use with analog computers and were not used with the flexibility of modern units. The range of operational-amplifier usage began to expand toward the present spectrum of applications in the early 1960s as various manufacturers developed modular, solid-state circuits. These amplifiers were smaller, much more rugged, less expensive, and had less demanding power-supply requirements than their predecessors. A variety of these discrete-component circuits are currently available, and their performance characteristics are spectacular when compared with older units.