What are Operational Amplifiers?

Electronics is an extremely extensive area, where it has a multitude of components, each with its respective characteristic and application. With that in mind we will explain what an operational amplifier is, what the characteristics of an operational amplifier are and what are the applications of an operational amplifier, in addition to addressing what is an instrumentation amplifier. Come on, guys!

Operational amplifier: What is it?

The operational amplifier, also called by some op-amp, is nothing more than an integrated circuit (CI), capable of amplifying an input signal and as its name suggests, the operational amplifier is also capable of performing mathematical operations, such as for example sum, subtraction, derivation. integration and multiplication.

The structure of an operational amplifier is simple, as it has two input terminals, called an inverter terminal, identified by the negative sign (-), the other terminal which is the non-inverter, identified by a positive sign (+) and a terminal output, in addition to two other terminals that are also essences, so that one of these terminals is the positive supply (+ Vcc) and the other is the negative supply (-Vcc), as we can see in the image below:

The basic structure of an operational amplifier.

Among the operational amplifiers, the most common is the LM741, we will hardly find an electronics course that when talking about operational amplifiers does not mention the LM741, besides it we can also mention the LM393 and LM324.

Connection pins for operational amplifiers

Operational amplifier: Main features

The characteristics of an operational amplifier are many, so we can highlight as a characteristic of an operational amplifier the high gain in open loop, high frequency response, high input impedance, low output impedance and low-temperature sensitivity, this in real conditions, with some variations between the components.

Ideal amplifier:

Under ideal conditions, an operational amplifier has an open-loop infinite gain, infinite frequency response, infinite input impedance, zero output impedance and temperature insensitivity.

Operational amplifier: Operation

The operational amplifier is a compact electronic component, which has resistors, capacitors and transistors in its internal composition. Quite simply, when a signal is applied to the non-inverting input, this signal is not inverted and comes out amplified, but when a certain signal is applied to the inverting input, the signal comes out amplified and inverted.

It is important to note that the output voltage of the operational amplifier depends on the potential difference between the inverting and non-inverting inputs, multiplied by the amplifier’s respective open-loop gain so that the maximum output voltage will be the amplifier’s supply voltage. , and the amplifier has this value in its output when the operational amplifier saturates.

Another detail that is important to highlight is the gain of the operational amplifier, which can be controlled and that to find it is enough to find the relationship between the value obtained at the output by the value of the input of the operational amplifier, that is, just divide the value obtained at amplifier output through its respective input.

What are Operational Amplifiers?

Operational amplifier: Polarization methods

After knowing a little more about what an operational amplifier is, what its characteristics are and how it works, we can know what are the operational amplifier’s operating modes, which are:

  • No Feedback;
  • Positive Feedback;
  • Negative Feedback;

Operational amplifier without feedback

This feedback mode is known as open loop operation, as it uses the amplifier gain that is stipulated by the manufacturer, that is, it is not possible to control the amplifier gain. This type of operation is commonly used in comparator circuits.

Operational amplifier without feedback.

Operational amplifier with positive feedback

Positive feedback is a closed-loop operation mode, when the positive input is connected to the output of the operational amplifier, via RF. The gain of the operational amplifier is obtained through the design and has the disadvantage of instability in the circuit, so it is widely applied in oscillating circuits.

Operational amplifier with positive feedback.

It is important to note that the operational amplifier operating with positive feedback does not work as a signal amplifier, because its response is not linear.

Operational amplifier in negative feedback

The operational amplifier operating in negative feedback is the most important and used in circuits involving operational amplifiers, note that this type of feedback in contrast to positive feedback, as you see that the output of the operational amplifier is reapplied to the inverter input via RF.

As with positive feedback, this mode of operation has the characteristic of closed loop, that is, the gain is determined by R1 and RF, and can be defined by the designer. We must highlight that it is in the negative feedback that the virtual short circuit takes place, where basically the signal that is applied to the non-inverting input is the same as in the inverting input.

Operational amplifier with negative feedback.

The video that we will see below explains what the gain of a transistor is, and how we can find this gain, so that you can understand a little more about the characteristics of a transistor, because after all we can make amplifiers like transistors.

Operational amplifier: Main applications

There are many applications for operational amplifiers, among which we can highlight the following applications in addition to those mentioned above:

  • Inverter Amplifier;
  • Summing Amplifier;
  • Non-Inverter Amplifier;
  • Differential Amplifier;
  • Differentiator;
  • Integrator;
  • Isolator (buffer);
  • Active Filters.

We finished one more article and we hope to have helped clarify doubts related to operational amplifiers. If you have any questions or curiosity about the subject, leave it in the comments and we will answer it!