Operational Amplifier

The term operational amplifier, or opamp for short, was coined in 1947 by John R. Ragazzini to denote a special type of amplifier that, by proper selection of its external components, could be configured for a variety of operations such as amplification, addition, subtraction, differentiation, and integration. The first applications of op amps were in analog computers. The ability to perform mathematical operations was the result of combining high gain with negative feedback.

Early op amps were implemented with vacuum tubes, so they were bulky, power-hungry, and expensive. The first dramatic miniaturization of the op amp came with the advent of the bipolar junction transistor (BJT), which led to a whole generation of operational amplifier modules implemented with discrete BJTs. However, the real breakthrough occurred with the development of the integrated circuit (IC) opamp whose elements are fabricated in monolithic form on a silicon chip the size of a pinhead. The first such device was designed by Robert J. Widlar at the ‘Fairchild Semiconductor Corporation’ in the early 1960s. In the year 1968 Fairchild introduced the op amp that was to become the industry standard, the popular μA741.

Since then the number of operational amplifier families and manufacturers has swollen considerably. Nevertheless, the 741 remains one of the most popular types in spite of competition from devices of comparable cost but superior performance because of its enduring popularity and the fact that it is the operational most widely documented op amp in the literature, we shall use it as a vehicle to Amplifier illustrate general operational amplifier principles and also as a yardstick to assess the relative Fundamentals merits of other op amp families. However, we shall not hesitate to turn to other operational amplifier types if they prove better suited to the application at hand. Operational amplifiers have made lasting inroads into virtually every area of analog and mixed analog-digital electronics. Such widespread use has been aided by dramatic price drops. Today, the cost of an op amp that is purchased in volume quantities can be comparable to that of more traditional and less sophisticated components such as trimmers, quality capacitors, and precision resistors. In fact, the prevailing attitude is to regard the operational amplifier as just another component, a viewpoint that has had a profound impact on the way we think of analog circuits and design them today.

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