Transistors in Switching Circuits

It is proposed to discuss some of the properties of transistors which are applicable to switching or pulse-type circuits, to develop elementary analysis methods and to describe a few circuits. T h e bounds or limits of the field of switching are difficult to define. T h e common thread usually involves definite states of being as "open or closed", "off or on", "0 or 1", and so on, rather t h a n a continuum of conditions. E v e n when consideration is given to more than two states, the thought involves distinct recognition of each state. T h e field is termed to be non-linear in distinction to linear manipulation of information. Any number of anomalies in definition m a y be raised. Without attempting either to define or to limit the field, some of t h e functions which are often employed are: wave form generation, as rectangular pulses, sawtooth waves, etc.; memory or storage which m a y 1207 3 238 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1952 be for short, intermediate or long periods and involves the retention of information for subsequent use; operations involving addition, subtraction, multiplication and division; translation of information from one form or code to another; gating, involving the routing of signals according to a predetermined pattern or set of conditions; regeneration of signals in amplitude and wave form; delay, which may be thought of as a form of storage; and timing. Some of these functions are simple; others result from fairly complex structures of simpler functions.