Power amplifiers: Classification

Chapter 2: High Power Amplifiers

Sub point 2.2

Classification:  Class  A;  Class  B,  Class AB  and  Class  C

• Classification / Types of power amplifier

Power amplifiers are classified on the basis of flow of collector current for applied input signal (on the position of Q point / operating point) as follows:

1 Class A amplifiers

2 Class B amplifiers

3 Class AB amplifiers

4 Class C amplifiers

 

 

Parameter	Class A	Class B	Class AB	Class C
Position of Q point on load line	Q point is at the centre of load line.	On X axis	Just above X axis.	Below X axis.
efficiency	lowest efficiency 25% to 50%	Above 78.5%	Between 50 to 78.5%	Above 95%
Conduction Angle	Conducts for (3600) full cycle of input signal	(1800) half cycle of input signal.	Greater than 1800 and less than 3600	Less than 1800 of input signal.
Crossover Distortion	No	More than class A	Low	More than A,B and AB
Power dissipation	Very high	Low	Moderate	Very low
O/P	100%	50%	Between 50 to 100%	Less than 50%
O/P waveform
Application	Outdoor musical system	Audio power amplifiers	RF amplifier	Audio power amplifier