Classification of Power Amplifier

• Power amplifiers are generally  used to increase the power strength of  input signal waveforms. It is also termed as  large signal amplifiers, because of  providing a large level of power signal at the output stage.

• Simplified block diagram of Power Amplifier system. 

 Based on the type of device attached to it, power amplifiers can be classified into the following categories:

1. Audio Power Amplifiers

2. DC Power Amplifiers

3. RF Power Amplifiers

Audio Power amplifiers are employed for amplifying the magnitude level   of a weak input signal. These are mainly applying for a speaker driven circuitries of TV, mobile phone etc. The output level of an audio power amplifier varies from a few mill to thousand watts. 
In the case of Wireless transmissions modulated waves to be broadcasted over long distance through the atmosphere. So the signal strength and transmission range depends on the power magnitude of signals provided to the antenna. In such situations Radio Frequency Power amplifiers are utilized to boost the power level  of modulated waves to a higher level in order to reach the desired   destination distance. 

DC Power amplifiers are employed to increase the power magnitude of Pulse Width Modulated waveforms. They are applied in electronic and electrical circuitries which require a higher amount of power to drive devices such as motors, actuators etc. It receives input from devices like microcontrollers then amplifies its power and fed back motors ,actuators etc. 

RF Power amplifiers used to amplify analog signals are termed as class A, B, AB or C types, where as in PWM it is named as class D, E, F etc.The generally applied power amplifiers are classes A, B, AB or C, which are the ones employed in audio amplifier circuitries .
Amplifiers are categorized  as Class A, Class B, Class AB and Class C Amplifiers depending on the mode of operation  ,which is also based upon the input signal cycle during which collector current is estimated to flow.