Analysis and design of transistor resistor logic (TRL) circuit for digital computers

Abstract

The object of this project is to analyse and to develop design procedures for a Transistor Resistor Logic (TRL) circuit to be used later for the construction of a 15 NOR circuits Teaching Kit (Dan-Gal) to be used for demonstrations of some Boolean Algebra principles. The basic circuit consists of ONE transistor and a number of resistors. This circuit may then perform the NOT, OR and AND functions. 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. Calculated and measured TURN – ON, TURN – OFF and STORAGE times values were performed on 0C83 transistor in order to understand better how and to what extent the values of collector current and base current etc. in the d.c. equations would affect the switching times of the transistor. A procedure has been followed to optimise for minimum required transistor base current. A solution was tried to obtain an ‘optimized’ value to build a NOR circuit of fan-in of 4 and fan-out of 1. Some methods have been also discussed to show how speed-up circuits can be used to give better switching times. Comparison of performance has been made between a NOR circuit used by Lan-Dec Computer Teaching Kit and the one designed by the theory outlined in this paper. The validity of the theory was tested on the Dan-Gal,- Educational Kit built for this purpose by programming some logic functions.