An Extended Topology of Parallel-Circuit Class-E Power Amplifier to Account for Larger Output Capacitances

This paper presents a modified parallel-circuit class-E amplifier that accommodates devices with larger output capacitances, recovering the class-E operating conditions. The finite inductor in the parallel circuit topology is replaced by a more suitable network composed of a series inductor and additional subharmonic resonators. Analysis of the class-E amplifier allows to determine the required frequency-domain response of this new network. Derivation of the circuit elements of the proposed network is shown in detail, and a design procedure for this modified class-E is provided. The analysis is validated by simulation and design of a test board. Measurements of the test board showed a drain efficiency of 80.7%, power-added efficiency of 78.6%, and output power of 4.91 W at 434 MHz, exhibiting levels of efficiency similar to that obtained by other amplifiers using the same device, but at much lower frequencies. According to the authors' knowledge, this study represents the first systematic approach to design class-E power amplifers at UHF using devices with larger
$C_{\rm OUT}$
by taking into account the use of arbitrary finite-feed class-E topologies.