Analysis of class-F and inverse class-F amplifiers

Power Balance in High Efficiency PAs

“…Similar result is theoretically obtained swapping voltage and current, as in the "inverse Class F" amplifier [5]. This is only an idealised approach.…”

The class-E/F family of ZVS switching amplifiers

“…Rearranging (9) (11) (12) In the high-efficiency case, this can be shown to give identical results as the well-known class-E result [6] (13)…”

“…Class F and its recently popularized dual inverse class F (class ) [10]- [12] have been developed primarily as a means of increasing saturated performance of class-AB and class-B designs. As a result, the attainable operating frequencies are somewhat higher, e.g., [5], [13] than those for class-E circuits, but the performance limitations due to the tuning requirements [14], [15] and the lack of a simple circuit implementation, e.g., [16], suitable for nearly ideal switching, make class F a poor alternative at frequencies where a lumped-element class E can be implemented.…”

High-Efficiency, Class-E RF Power Amplifiers

“…This family allows the reduced circuit complexity of class-E with waveforms approaching the efficiency of inverse class-F [5], while at the same time absorbing the transistor output capacitance into the circuit as in class-E. Furthermore, the tolerance for large transistor output capacitance can be several times that of class-E for many amplifiers in this family, potentially allowing for higher frequency operation using the same transistor technology.…”