The period centered on achieving high-efficiency switching power conversion, with Class E and related tuned topologies driving RF and power applications. Device-level innovations—vertical-channel high-voltage field-effect transistors and insulated-gate transistor structures—paired with generalized, compact modeling methods, such as sampled-data representations, to streamline design and analysis. Extensions of Class E theory to practical constraints, including finite DC-feed inductance, bridged theory and real-world implementations, fostering a more integrated design framework.