Analytical Design of Resistor-Coupled Transistor Logical Circuits

The object of this paper is to analyze and to develop design procedures for a resistor-coupled transistor circuit used in the mechanization of logical operations. The basic circuit consists of one transistor and a number of resistors. This circuit performs the OR function followed by the NOT function or the AND function followed by the NOT function. With these compound functions mechanized it is possible to build any logical system. The first requirement for operation of this circuit is that the transistor must be saturated if one or more inputs are low. The second requirement is that the transistor must be cut off if all of the inputs are high. A ``worst case´´ analysis is performed for each of these requirements. Three types of solutions are described and discussed: general purpose, intermediate (flexible), and special purpose. The general purpose design uses one standard stage for the mechanization of an entire logical system. The special purpose design is tailored to fit a complete logical system. If any logical change is made, a large part of the circuitry must be redesigned. An intermediate (flexible) design uses different stage designs, having different numbers of inputs and outputs. Procedures are developed for the design of the general purpose system in two ways: hand computation with a slide rule; computation on a small digital computer (Burroughs E101). Procedures are developed for the design of the intermediate flexible system using hand computation.