This article begins a series of lectures on analogic electronics.

It assumes that the reader knows basics of electrical engineering and knows behaviors of electrical and electronical components like resistors, capacitors, inductors, diodes and transistors.

The course focuses *Operational Amplifier* and circuit configurations that use it.

The reason is that *Operational Amplifier* has unique characteristics that allow you to use it as the heart of a multitude of analog circuit configurations.

The *Operational Amplifier*, also known as *Op Amp*, is so called because it can be used to make simple circuit configurations performing mathematical operations on analog electrical signals: addition, subtraction, multiplication, division, inversion of the sign, integration, derivation, logarithm and antilog.

But this is only a part of the circuits based on *Op Amp*.

Others are: amplifiers, voltage-current converters, current-voltage converters, comparators, oscillators, active filters, ADCs and DACs.

The *Operational Amplifier* accepts two input signals and returns, in output, a voltage that corresponds to the amplification of the difference between the two input voltages.

For this reason *Op Amp* is a kind of *Differential Amplifiers*.

In the following we will focus on key features of *Op Amp* to understand how they can enable us to achieve many of the circuits mentioned above.