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Is Op-Amp Still Relevant Today?




In today's age of Internet of Things, machine learning, artificial intelligence, cloud computing, and so on, one might wonder what place the operational amplifier has in the current state of affairs in technology. Is it still really relevant that it's worth continuing to learn them in school or by one's own effort? My answer is yes, and this takes us back to the early beginnings of why the operational amplifier was invented in the first place.

To those who are familiar with its history, we recall that it was Harold Black's idea in the early 20th century of negative feedback that the operational amplifier takes it root back to its very beginning. The first Integrated Circuit (IC) op-amp didn't come to us until the mid-1960, as the first operational amplifiers were in the form of vacuum tubes and discrete components.

In the early days of amplifiers in the beginning of 1900's, these devices are notoriously non-linear and distorts a lot in telecommunications network where it was used extensively during that time. It makes the signal, or the voice one hears on the telephone, very inconsistent and noisy, rendering the whole system unreliable. Harold Black proposed that if he has an amplifier that has a very large forward gain, takes its output or a portion of it back to its negative input, he will be able to make his amplifier linear and more predictable, drastically reducing the distortion and noise inherent in the amplifiers. This idea was game changing, and its effects far reaching that we still benefit from it up to the present.

When I talk to some engineering students about op-amps, what I invariably get from them about their understanding of op-amp is its common textbook ideal characteristics, like the infinite open-loop gain, zero offset, etc. Not a lot appreciates that what the op-amp really does so well is its ability to produce a very predictable output in terms of the gain (not the open loop gain), even though the open loop gain of the amplifier itself can vary a lot. Its manufacturing distribution can be such that its open loop gain may range from a few thousand to a few millions. If wired as a negative-feedback amplifier with a gain of 2 for example, one can reasonably expect that it will remain to have that gain under different conditions like temperature or supplies. The closed-loop gain becomes independent of the amplifier itself, rather, it is now is a function of the resistors we use with it. Now isn't that truly amazing!





Op-Amp, as we know them today, is still widely used in many electronics applications and still the backbone of analog and mixed signal circuits. We still need to amplify and condition the analog signals that we see around us before we convert them to the digital signal that our computers understand. These analog signals are in the raw form of sound, images, temperature, pressure, gas, and host of many things that our planet consists of. In fact I think the op amp will still be around for many years to come.



Reference:
Op Amp History, Op Amp Applications Handbook, Analog Devices Edited by Walter Jung, 2002
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