|Class A-Circuit Diagram|
In this configuration, the Class A amplifier uses the same transistor for both halves of the output waveform and due to its biasing arrangement the output transistor always has current flowing through it, even if there is no input signal. In other words the output transistors never turns "OFF". This results in the class A type of operation being very inefficient as its conversion of the DC supply power to the AC signal power delivered to the load is usually very low.
Generally, the output transistor of a Class A amplifier gets very hot even when there is no input signal present so some form of heat sinking is required. The DC current flowing through the output transistor (Ic) when there is no output signal will be equal to the current flowing through the load. Then a pure Class A amplifier is very inefficient as most of the DC power is converted to heat.
|Class A Output Waveform|
----It has low efficiency of less than 40% but good signal reproduction and linearity
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