Effects of the collector current fall time on the class E tuned power amplifier

The previous publications on the class E tuned power amplifier have analyzed its idealized model in which the collector current fall time is zero. The purpose of this paper is to present the equations governing the operation of the amplifier when the collector current fall time during the on-to-off transistion of the transistor is an appreciable fraction of the signal period. A current-source model of the transistor with a linearly decreasing collector current during the fall time is used. The following basic amplifier parameters are determined: the waveforms of the collector current, the collector-to-emitter voltage, the instantaneous power dissipated in the transistor, the optimum values of the load-network components, the output power, the power-output capability, and the collector efficiency. The decrease of the collector efficiency is, e.g., 10 percent at 60 deg fall time. Experimental results are also given. The paper shows the behavior of the class E amplifier at higher operating frequencies and provides more accurate circuit design procedure.