RF Power Amplification 101: Amplifier Classes

RF power amplification (PA) is the key to achieving wireless application requirements, such as in ubiquitous communication technologies and radar. To understand the interplay of tradeoffs with requirements, including efficiency and power consumption, range, and linearity, the first in this series of articles on RF PA essentials dealt with basic waveform shapes and the formulae for calculating power supplied, RF output power, and efficiency. That article assumed idealities in waveform shapes — no over- or undershoots — and an ideal transistor.

We continue with these assumptions in this, the second part, as we look at the amplification mechanism, how amplifiers can be classified by circuits needed to generate various waveform shapes, and how the output waveform affects efficiency.