Symmetrical transistor logic
Ryan Baker · 1958
This paper discusses symmetrical transistor switching circuit techniques. The circuitry is designated "symmetrical circuits" because the basic circuits employ both p-n-p and n-p-n transistors in approximately equal numbers which result in networks that exhibit a high degree of operational and topological symmetry. The major practical advantage of this circuitry over other types lies in the ease with which basic circuits may be integrated into a digital system. This advantage is made possible through, 1, keeping the circuit configurations flexible (to satisfy many different system applications), 2, worst-case circuit design with regard to component stability and system loading requirements, 3, use of only standard commercially available components, and 4, insisting that all present-day circuit designs be applicable to known future device trends. The major criticism of the symmetrical circuit techniques is that the circuits require a greater number of components for a specific equipment than do other types of circuitry that can be engineered to build the specific system. However, it is felt that this criticism is not justified in this case for two reasons. They are: 1, The additional cost of components required for symmetrical logic is more than counter-balanced by the shorter system realization time required. This is particularly true for an establishment, such as the Massachusetts Institute of Technology Lincoln Laboratory, that is engaged in system research and development. And, 2, that symmetrical logic techniques are more adaptable to future developments in the device, circuits and system area than other types of circuit logic.