Analog electronics is one of the most important branches of electrical engineering, which has become a stepping stone for the transition from resistors, rheostats and ammeters to digital “measurement”. Using combinations of many electrical components and forming complex circuits, analog electronics made it possible to use their achievements to create simple digital appliances. Today, analog electronics is the basis for the circuitry of complex 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 node receiving the signal is a large value of the gain.
Integral performance implies that the operational amplifier is located specialized in one of the working blocks of the chip. In circuitry, this device, like all other elements, received a special designation. As a rule, in schematic diagrams, an operational amplifier is designated as a large triangle. Recently, however, you can find an alternative symbol for the amplifier - a rectangle with a small triangle inside. Most likely, this designation was introduced to simplify the image of the device in 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, an 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 control systems of many physical quantities (in particular, at weather stations).
The principle of operation of an operational amplifier is often compared with a pharmacy balance, the arrow of which deviates in the direction where the load on the cup is greatest. Only for the operational amplifier it is necessary to mark one of the cups with a “+” sign, the second - “-”, 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 at the direct input is greater than at the inverse, then a positive voltage is generated at the output (otherwise, a negative voltage).
Returning to the designation of operational amplifiers in principle electrical circuits, it is worth noting that direct input is often indicated by a “+” sign, and an inverse - “-”. However, such characters are not always used! Sometimes they do not put signs at the entrances on the circuits, but instead, the inverse input is marked as a small circle.
In order to reduce the sensitivity of the operational amplifier to technical fluctuations of the input electrical signal, OOS is introduced into the operational amplifier - negative feedback. Due to the use of such a component of the circuit as connecting the output to the inverse input through a special resistor, slight deviations from the given input signal are not taken into account by the operational amplifier during operation.
Sometimes, for the operation of the operational amplifier in the circuit diagrams of complex devices, positive feedback is used, 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 with unipolar, there and with a bipolar power source.