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complementary metal oxide semiconductor -CMOS – process


CMOS (complementary metal-oxide semiconductor) is the semiconductor technology used in the transistors that are manufactured into most of today’s computer microchips.

Semiconductors are made of silicon and germanium, materials which “sort of” conduct electricity, but not enthusiastically.

Areas of these materials that are “doped” by adding impurities become full-scale conductors of either extra electrons with a negative charge (N-type transistors) or of positive charge carriers (P-type transistors). In CMOS technology, both kinds of transistors are used in a complementary way to form a current gate that forms an effective means of electrical control.

CMOS transistors use almost no power when not needed. As the current direction changes more rapidly, however, the transistors become hot. This characteristic tends to limit the speed at which microprocessors can operate.

CMOS stands for Complementary metal–oxide–semiconductor,CMOS is also sometimes referred to as complementary-symmetry metal–oxide–semiconductor. The words “complementary-symmetry” refer to the fact that the typical digital design style with CMOS uses complementary and symmetrical pairs of p-type and n-type metal oxide semiconductor field effect transistors (MOSFETs) for logic functions.

Two important characteristics of CMOS devices are high noise immunity and low static power consumption. Significant power is only drawn when the transistors in the CMOS device are switching between on and off states. Consequently, CMOS devices do not produce as much waste heat as other forms of logic, for example transistor-transistor logic (TTL). CMOS also allows a high density of logic functions on a chip.





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