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Operational Amplifier                                                                         

An operational amplifier, is usually referred to as an op-amp. These devices have very high gain. On the left are the input terminals and on the right side are output terminals. The + and - Signs above have nothing to do with supplies. These op-amp are used for signal amplification. 

The positive terminal in above figure is "Non Inverting Terminal" and negative terminal is called inverting terminal. There is a Output Terminal on right and positive and negative supplies for supplying required strength for amplification as in figure above. In its general usage, the output of the op-amp is controlled by negative feedback which gives the magnitude of its output voltage gain, input impedance at one of its input terminals and output impedance. A Comparator is a device used to compare two signals and indicate which one of them is greater. When an Op-amp is used without any feedback an minor i/p signal makes amplifier's o/p to switch between its saturation limits hence this property is used in making comparators.

Amplifiers are commonly classified by the conduction angle sometimes known as 'angle of flow' of the input signal through the amplifying device.

Class A

We can use these type of amplifiers for Headphones. This type of amplifier is most commonly used in for low-power applications. Where efficiency is not considered,  amplifiers are made as Class A amplifiers which means that the output devices are always in the conduction region. Class A amplifiers are less complex than other class amplifiers, but are inefficient.

Class B

In Class B, there are two output devices each of which conducts alternately for exactly 180 deg or half cycle of the input signal.

Class AB

Conduction angles vary from 180 degrees upwards. Found in low frequency amplifiers .

Class C

This class is popular for high power RF amplifiers, Class C is defined by conduction for less than 180° of the input signal.

Class D

These use switching to achieve a very high power efficiency

 

Operational Amplifiers Manufacturers