Design Aspects of VLSI for Computer Logic

Interrelations among device technologies, circuit techniques, layout design, computer-logic characteristics, and system performance were clarified by analyzing several key factors which determine effective circuit performance in system environments. Computer-logic characteristics which determine the effective power of complementary circuits were investigated. This was done by evaluating "k," which is defined by the average switching period of the circuits in a system divided by the system delay time. The value of several tens to 200 was obtained as the it for conventionally designed computer logic. Load-driving capabilities for various circuits were evaluated to clarify the effects of circuit technique and device technology. Estimation of wire capacitance was made possible by obtaining empirical relationships which gave the wire length, and by developing a capacitance computing program using a finite element method. It is shown that significant merit in wire capacitance should not be expected from the semi-insulating substrate structure of GaAs LSI\´s. Finally, differences in logical-function capabilities among various circuits were clarified based upon empirical results. These results provide a basis for evaluating and optimizing the overall effects of introducing new technologies, as well as for interfacing computer-logic and VLSI design realms.