Abstract: The subassembly of the present invention includes three pairs of aligned steering diodes and a single thyristor situated between spaced apart conductive heat sink plates. The subassembly is configured to fit into a standard 3-lead transistor outline package by arrangement of the semiconductors and shaping of the conductive plates. In one embodiment, the plates are square, and the components are arranged such that the diode pairs and thyristor are proximate the corners of the plates. In another embodiment, a "T" arrangement is utilized for the components which are situated between "H" shaped plates.