Junction transistor switching circuits for high speed digital computer applications

Abstract

Summary form only given. This paper describes junction transistor switching circuits capable of reliable operation at a rate of 1,000,000 pps. These circuits consist of a flip-flop, a gated pulse amplifier and diode gates which together provide the basic building blocks of the arithmetic section of a digital computer. The designs are based on transistor types, such as alloy junction and surface barrier transistors, which exhibit low and consistent values of extrinsic resistances. As a result, complete interchangeability is obtained from a simple circuit. Several suitable high frequency alloy junction transistor types, both NPN and PN P, are available commercially in large quantities at relatively low cost. A minimum alpha cutoff frequency of 5 megacycles and a minimum alpha of 0.95 are the most important transistor requirements. Special devices such as Zener diodes are not required. Flip-flop rise and fall times of 0.3 microsecond and 0.2 microsecond, respectively, are obtained by the use of large drive currents, low values of collector load resistance, emitter followers to reduce lo~ding effects, and by preventing transistor saturation. High speed diode gates and gated pulse amplifiers which are relatively insensitive to changes in gating levels are employed.