Switchmode DC—DC power converters using one or more non-Silicon-based switching transistors and a Silicon-based (e.g. CMOS) controller are disclosed. The non-Silicon-based switching transistors may comprise, but are not necessarily limited to, III-V compound semiconductor devices such as gallium arsenide (GaAs) metal-semiconductor field effect transistors (MESFETS) or heterostructure FETs such as high electron mobility transistors (HEMTs). According to an embodiment of the invention, the low figure of merit (FoM), _FET, of the non-Silicon-based switching transistors allows the converters of the present invention to be employed in envelope tracking amplifier circuits of wireless devices designed for high-bandwidth technologies such as, for example, EDGE and UMTS, thereby improving the efficiency and battery saving capabilities of the wireless devices.