Implementation of class-E/F3 power amplifiers based on the variations of the MOSFET grading coefficient, built-in potential and output capacitance along with their roles in MOSFET selectivity

In this paper, a theoretical analysis of the class-E/F-3 power amplifier based on the variation of the grading coefficient m(1) and its vital role in MOSFET selectivity to operate safely under given design specifications is presented while the nonlinearity of the drain-to-source capacitance is considered. Moreover, the importance of V-bi and C-jo in designing the class-E/F-3 amplifier is investigated. To clarify how the grading coefficient m(1) and the other mentioned parameters can directly influence the power amplifier performance and also its elements, these MOSFET parameters are considered as the independent variables of the calculated equations and consequently define the horizontal axis of the obtained plots. Accordingly, as the grading coefficient increases, the maximum switch voltage increases and values of the output power and output power capability decline. Moreover, to prove the reliability of the carried-out analysis in selecting proper MOSFETs, the performances of three amplifier samples utilizing IRF510, IRFZ24N, and 2SK2504 MOSFETs with different grading coefficient m(1) and almost similar V-bi and C-jo are studied. Then, by comparing the results of amplifiers with three MOSFETs, IRF510, IRF530, and IRF540, with similar grading coefficient and different values of V-bi and C-jo, the significance of considering the values of V-bi and C-jo is investigated. Eventually, three amplifiers with 2SK2504, IRF510, and IRF530 MOSFETs have been simulated, implemented, and tested and measurement results agreed well with the theoretical and simulation results.