RF Power Amplifier, 2nd Edition

Chapter 5Class E Zero-Voltage Switching RF Power Amplifiers

5.1 Introduction

There are two types of Class E power amplifiers [1–97], also called Class E dc–ac inverters: (1) Class E zero-voltage switching (ZVS) power amplifiers, which are the subject of this chapter, and (2) Class E zero-current switching (ZCS) power amplifiers. In Class E amplifiers, the transistor is operated as a switch. Class E ZVS power amplifiers [1–35] are the most efficient amplifiers known so far. The current and voltage waveforms of the switch are displaced with respect to time, yielding a very low-power dissipation in the transistor. In particular, the switch turns on at zero voltage if the component values of the resonant circuit are properly chosen. Since the switch current and voltage waveforms do not overlap during the switching time intervals, switching losses are virtually zero, yielding high efficiency.

We shall start by presenting a simple qualitative description of the operation of the Class E ZVS amplifier. Although simple, this description provides considerable insight into the performance of the amplifier as a basic power cell. Further, we shall quickly move to the quantitative description of the amplifier. Finally, we will present matching resonant circuits and give a design procedure for the amplifier. By the end of this chapter, the reader will be able to perform rapid first-order analysis as well as design a single-stage Class E ZVS amplifier.

5.2 Circuit Description

The basic circuit ...