RF Power Amplifier, 2nd Edition

Chapter 6Class E Zero-Current Switching RF Power Amplifier

6.1 Introduction

In this chapter, a Class E RF zero-current switching (ZCS) power amplifier [1–6] is presented and analyzed. In this amplifier, the switch is turned off at zero current, yielding zero turn-off switching loss. Therefore, this circuit is also called an inverse Class E amplifier. A shortcoming of the Class E ZCS amplifier is that the switch output capacitance is not included in the basic amplifier topology. The switch turns on at a nonzero voltage, and the energy stored in the switch output capacitance is dissipated in the switching device, reducing the efficiency. Therefore, the upper operating frequency of the Class E ZCS amplifier is lower than that of the Class E ZVS amplifier.

6.2 Circuit Description

A circuit of a Class E ZCS RF power amplifier is depicted in Fig. 6.1(a). This circuit was introduced in [1]. It consists of a single transistor and a load network. The transistor operates cyclically as a switch at the desired operating frequency . The simplest type of load network consists of a resonant inductor connected in series with the dc source , and an -- series-resonant circuit. The resistance