How is the efficiency of a Class A amplifier typically characterized?

In a Class A amplifier, the efficiency is characterized as very low, typically around 20-30%. This low efficiency arises because the amplifier conducts over the entire input signal cycle, meaning it continuously draws current from the power supply, even when there is no input signal. As a result, a significant amount of power is dissipated as heat rather than being converted into useful output power. This heat generation necessitates adequate heat sinks and thermal management to prevent damage to the amplifier components.

While Class A amplifiers are known for their excellent linearity and sound quality, this comes at the cost of efficiency. The trade-off between high fidelity in output and low efficiency is a fundamental characteristic of Class A amplification.