This guide to the theory and practice of RF power amplifier (PA) design for modern communications systems aims to help readers tackle PA design with confidence and save time in determining the cause of malfunctioning hardware. The book explores a unified approach to the classification of higher amplifier modes based on overdrive considerations. The text contains a complete survey of RF PA efficiency enhancement and linearization techniques and aims to help the reader design suitable matching networks which provide correct fundamental harmonic terminations for conventional high efficiency PA modes. It also provides an understanding of the class D, E and F modes and their feasibility at microwave frequencies and uses envelope simulation techniques to analyze the effects of distortion in overdriven PAS. Finally, the text discusses the maintenance of high efficiency operation at low points in an amplitude modulated signal envelope including detailed coverage of the Doherty, Chireix and Kahn techniques, it explores the possibilities and limitations of linearization methods and analyzes PA stability and oscillation problems.