Abstract: To facilitate manufacture and assembly of the structural support and electrical connections of a composite driver and power semiconductor element, the metal base plate of the composite structure carries the driver power element, and the driver element is supported, in insulated relation with respect thereto, on a post formed as a rotation-symmetrical body, typically a flat-ended cylinder or a headed wire, and carried through the base plate, for example by a glass seal. Each one of the driver and power elements may, themselves, be composite integrated circuits, the power element being preferably a Darlington unit, the driver element including transistor and a Zener diode and associated resistors.