ABSTRACT
Integrated circuits (ICs) are classified according to their levels of complexity: small-scale integration, medium-scale integration, large-scale integration (LSI) and very large-scale integration (VLSI). They are also classified according to the technology employed for their fabrication, complementary metal oxide semiconductor. In principle, the basic gates are sufficient for the design of any digital integrated circuit, no matter how complex. In practice, modifications are necessary in the basic gates and medium-scale integration circuits like flip-flops, registers, and adders, when such circuits are to be employed in LSI or VLSI design. Design rules specify minimum device dimensions, minimum separation between features and maximum misalignment of features on an IC. Such rules tend to be process and equipment dependent. Gates are the basic building blocks in digital integrated circuits. Small-scale integrated circuits are essentially gate circuits, and medium-scale integrated circuits are circuits employing several gates. Gates, in turn, are based on inverters and can be realized from inverter circuits with some modifications.
