CHAPTER 10 Class-G Power Amplifiers Now comparing the two-pole B C amplifier with Figure 10.19 (the A C amplifier) the above- transition (30 W) THD at 10 kHz of the former is lower at 0.005% compared with 0.008%. As I have demonstrated before, proper use of two-pole compensation can give you a Class-B amplifier that is hard to distinguish from Class-A--at least until you put your hand on the heat-sink. FURTHER VARIATIONS ON CLASS-G This by no means exhausts the possible variations that can be played on Class-G. For example, it is not necessary for the outer devices to operate synchronously with the inner devices. So long as they turn on in time, they can turn off much later without penalty except in terms of increased dissipation. In so-called syllabic Class-G, the outer devices turn on quickly but then typically remain on for 100 ms or so to prevent glitching (see Funada and Akiya, 1984 for one version). Given the good results obtained with straight Class-G, this no longer seems a promising route to explore. With the unstoppable advance of multichannel amplifier and powered subwoofers, Class-G is at last coming into its own. It has recently even appeared in a Texas ADSL driver IC. I hope I have shown how to make it work, and then how to make it work better. I modestly suggest that this might be the lowest distortion Class-G amplifier so far. REFERENCES Feldman, L. , (August 1976). Class-G high efficiency hi-fi amplifier , Radio Electron. , p. 47 . Funada, S. and Akiya, H. , (October 1984). A study of high-efficiency audio power amplifiers using a voltage switching method , JAES , 32 (10) , p. 755 .