TABLE OF CONTENTS A logical starting point for a book on RF power amplifier design would be to define what a power amplifier (PA) actually is. A technical definition might be an amplifier which is designed to deliver the maximum power output for a given selection of active device. Such a definition is useful in that it emphasizes that many of the techniques described in this book will be of interest to small signal amplifier designers. For example, the problem of obtaining low noise performance and also maximum dynamic range from an amplifier used in the front end of a receiver could be considered to be a PA design problem, and the techniques described in Chapter 2 would be applicable.
But in practice, by a PA, we really mean an amplifier that can do damage to something. We are talking about a world of uncharacteristically high excitement in the RF lab, where attenuators and terminations get hot, and the life expectancy of expensive test equipment is greatly reduced. This means we are talking about RF outputs anywhere from the 1 watt level upwards. Above this level, we start to feel our amplifier RF output, even when safely dissipated in an attenuator. PAs are amplifiers whose outputs either directly or indirectly make an impact on the human sensory system.
Pyrotechnics notwithstanding, many power amplifier designs are simple extensions or modifications of linear designs. In the first place it will therefore pay to look at amplifiers in general, and to recall some of...
