Operational amplifier: description, principle of operation, application

Analog electronics is one of the most important parts of electrical engineering, which has become a stepping stone for switching from resistors, rheostats and ammeters to digital "measurement". Using combinations of many electrical components and forming complex circuits, analog electronics allowed using their achievements to compile the simplest digital electrical appliances. Today, analog electronics is the basis for the circuitry of sophisticated modern electrical appliances.

One of the devices of analog electronics is an operational amplifier, which is a complex multistage circuit using semiconductors. In integral form, this device has two inputs that invert each other. It is noteworthy that one of the properties of the inverse signal receiving unit is a large value of the gain.

Integral design implies that the operational amplifier is placed in a specialized one in the working blocks of the chip. In circuit design this device, like all other elements, received a special designation. As a rule, in operational diagrams, the operational amplifier is designated as a large triangle. However, recently you can find an alternative symbol for the amplifier - a rectangle with a small triangle inside. Most likely, such a designation is introduced to simplify the image of the device in the structural diagrams.

The use of operational amplifiers is very diverse today. These multi-stage instruments are used in a wide variety of amplifiers for various signals. In addition, the operational amplifier is often used in electrical signal generators, as well as in frequency filters for the audio range. In addition, the amplifier has become an indispensable device in the schemes of control systems of many physical quantities (in particular, at weather stations).

The operating principle of the operational amplifier is often compared with the pharmacy weights, the arrow of which deviates to the side where the load on the calyx is greatest. Only for the operational amplifier one needs to mark one of the cups with the "+" sign, the second one - "-", and replace the measured value with volts instead of grams. So, the amplifier compares the voltage module at one and the second input. If the potential difference on the direct input is greater than on the inverse, then the output forms a positive voltage (otherwise negative voltage).

Returning to the designation of operational amplifiers on the principle of electrical circuits, it is worth noting that the direct input is often denoted by the sign "+", and the inverse - "-". However, such symbols are not always used! Sometimes on schemes the signs at the inputs are not set, but instead the inverse input is marked in the form of a small circle.

In order to reduce the sensitivity of the operational amplifier to the technical fluctuations of the input electrical signal, an OOS is introduced into the operational amplifier-negative feedback. Due to the use of such a circuit component as the connection of the output with the inverse input through a special resistor, slight deviations from the specified input signal are not taken into account by the operational amplifier in operation.

Sometimes, for the operation of an operational amplifier, the principle circuit diagrams of complex devices use positive feedback, in which the positive input and output are connected through a specialized resistor. When using positive feedback, an interesting side effect appears - the "hysteresis loop".

In conclusion, we note that operational amplifiers are used both for unipolar and for bipolar power supplies.