Electronics is Fun

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 telecommunication...

Current source programs an output current as defined by the user, regardless of the load resistance. We know that when load resistance is larger, the voltage across it also increases. An ideal source would maintain a constant amount of current even if the load resistance changes, or in other words even if the output voltage changes. Such behavior describes a very good current source that has high output impedance. Remember, the output voltage changes, but very little or no change in output current. That means high output resistance or impedance. We use the term impedance when dealing with changes. Howland circuit in the figure is a classic current source circuit.   When R 1 is made equal to R 2 , R F equal to R 3,  the output current is given by V IN /R 1 where V IN is V 1 minus V 2 . A simple implementation is grounding V 2 and taking V 1 as the V IN . Figure 1 Basic Howland Current Source This circuit is such a clever manipulation of the op a...