CHAPTER 10 Class-G Power Amplifiers Audio Power Amplifier Design Handbook by Douglas Self Most types of audio power amplifier are less efficient than Class-B; for example, Class-AB is markedly less efficient at the low end of its power capability, while it is clear that Class-A wastes virtually all the energy put into it. Building amplifiers with higher efficiency is more difficult. Class-D, using ultrasonic pulse width modulation, promises high efficiency and indeed delivers it, but it is undeniably a difficult technology, and its linearity is still a long way short of Class-B. The practical efficiency of Class-D rests on details of circuit design and device characteristics. The apparently unavoidable LC output filter--second order at least--can only give a flat response into one load impedance, and its magnetics are neither