Circuits for Multiple Valued Logic -- a Tutorial and Appreciation

It has been stated often in the past that practical acceptance of multi-valued logic awaits the development of suitable electronic means for fabricating a sufficiently powerful and general purpose logic. Though the search for such means has proceeded in parallel with every other development in the multivalued field in the last thirty years, there is reason to believe that the pace is quickening and that success, by some measure, is sensibly upon us. In support of this contention I offer in a general sense the all-pervasive presence of the integrated circuit industry in which formerly inconceivable complexity is a current low cost reality. Another, less obvious, property of this industry is its continuing search for complex, more powerful, functional entities to integrate. As linear dimensions of physically attainable devices increase, their accessability (through traditional edge connections) rises in direct proportion. Obviously, however, the space for components rises as the square of the access dimension. This face coupled with a concurrent reduction in component scale through developments in photolithography, etc., greatly encourages the search for ever-increasingly-complex, less-access-limited products, which use area in trade for perimeter. Such is one potential for multi-valued processing. At the same time as these IC developments, and no doubt encouraged by them, there has been a rapid increase in the interest and accomplishment of circuit designers in the multi-valued area[l]A large variety of techniques and technologies have been exploited or are about to be. We have seen recent offerings, of direct interest to the multi-valued discipline, of the multiemitter bipolar technology of Transistor-Transistor Logic (T2L), of variations of the technology of COS MOS and of developments relating directly to the currentswitching designs of Emitter Coupled Logic (ECL). Shortly, we shall see evidence of the use of the recently developed Integrated Injection Logic (I2L) in multi-valued design. It is with these perspectives that the present paper is written. It is important for the multi-valued discipline that each of the practitioners of its various facets are truly aware of, and interact with, the developments of the others. With this in mind we will begin an overview of electronic circuitry whose goal it is to enhance the appreciation of non-specialists in the rapid technological development which surrounds them. We begin by reviewing some very basic properties of electronic devices, introduce a convention for drawing circuits which is a considerable aid in communicating and understanding, proceed to describe and interrelate global properties of available active (transistor) devices, then finally practice these basics on circuits typical of those you will see increasingly in the literature. The pace will be fast, the treatment unconventional, the scope distressingly broad. Our goal will be an improved appreciation of what has happened, and more importantly, an approach to understanding and appreciating more fully what is about to happen!