What is the distinguishing feature of a Class A amplifier?

A Class A amplifier is characterized by its ability to conduct for the entire 360 degrees of the input signal cycle. This means that it can amplify both the positive and negative halves of the waveform without any interruption or distortion. Because it operates in this manner, Class A amplifiers are known for their high linearity and low distortion, making them suitable for high-fidelity audio applications.

In practical terms, the operation of a Class A amplifier involves maintaining a continuous flow of current, ensuring that the output closely follows the input signal throughout the entire cycle. This continuous conduction is what allows the Class A design to deliver high-quality amplification but also typically results in lower efficiency compared to other amplifier classes. The ability to output across the complete range of the signal cycle is what fundamentally distinguishes Class A amplifiers from others that may only amplify portions of the signal.