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Wednesday, May 11, 2011

CMOS Logic Circuits

For many years, complementary MOS (CMOS) technology was available only in unit logic form, with several gates packaged together in a single dual in – line package (DIP), but it was not widely used in complex integrated circuits. CMOS requires that both NMOS and PMOS transistors be built into the same substrate, and the increased complexity and cost this represents were the primary reasons why CMOS technology was little used .as time passed ,however ,the size of transistors in ICs continued to decrease, so an ever – larger number of gates could be placed on a given size IC chip. By the early 1980s, the total power consumption of NMOS ICs was becoming prohibitive. The problem was so severe that it was hampering progress in increasing the density of ICs. To solve the static power dissipation problem, the microprocessor industry at this point rapidly moved to CMOS technology. Today, CMOS is the industry wide standard technology.
This chapter investigates the design of CMOS logic circuits, starting with characterization of the CMOS inverter, and follows with a discussion of the design of NOR,NAND,and complex gates  based on  CMOS reference inverter . 

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