The power amplifiers is said to be class A amplifier if the Q point and the input signal are selected such that the output signal is obtained for a full input cycle. For this, postion of the Q point is approximately at the midpoint of the load line.

For all values of input signal, the transistor remains in the active region and never enters into cutoff or saturation region. When an a.c input signal is applied the collector voltage varies sinusoidally hence the collector current also varies sinusoidally.

The collector current flows for 360 degree of the input signal. In other words, the angle of the collector current flow is 360 degree.The current and voltage waveforms for a class A operation are shown with the help of output characteristics and the laod line.

For full input cycle is obtained. Here signal is faithfully reproduced at the output without any distortion. This is an important feature of a class A operation. The efficiency of class A operation is very small.