Use of junction transistors in computer amplifiers

AN INVESTIGATION has been conducted to determine the applicability of junction transistors to carrier frequency summing amplifiers of the type commonly used, for example, in the a-c analogue computers of military fire-control systems. The general form of the summing amplifier is shown in Fig. 1. Usually, large amounts of negative feedback are employed to maintain a high computing accuracy. The techniques used in the design of low frequency vacuum-tube feedback amplifiers are well known and so there is a tendency to determine if they are applicable to an equivalent transistor amplifier. Recognizing the transistor as the only new circuit element, a knowledge of its circuit behavior is essential. This paper, therefore, describes briefly some of the basic problems confronting the designer of transistor feedback circuits. The problems were investigated from both an analytical and experimental point of view and lead to the evolution of one design philosophy which yielded satisfactory results when applied to the design of an experimental 5-stage amplifier utilizing transistors which were commercially available in mid-1954. Typical transistors are the type 2N34 and newer type 2N709.