| | | | Complementary Metal Oxide Semiconductor. This term, "metal oxide semiconductor" refers to the physical structure found in some field effect transistors - a metal gate electrode set on top of an oxide insulator, on top of a semiconducting material. A very widely used silicon and germanium based integrated circuit (IC) design, almost ubiquitous across all electronic products - most modern chips (termed "die" or "dice" in the industry) are now constructed on the CMOS basis. The CMOS IC is a type of transistor that, unlike other transistors, uses a combination of both NMOS (negative polarity) and PMOS (positive polarity) circuits connected together. Only one of these circuit types is on at a particular time (CMOS circuits dissipate power only when switching), meaning that a CMOS chip uses less power than an equivalent NMOS or PMOS chip and is very efficient, also emitting less energy in the form of waste heat. As a result of the latter, certain CMOS chips can run very fast without risking heat damage. CMOS circuitry is more dense than other design types with the same functionality. The charge in the circuit can also stay in one state over an extended period of time. CMOS circuits also show a high level of immunity to electronic noise. All of this makes CMOS ICs ideal for use in battery powered devies such as laptop PCs and PDAs for example. CMOS memory is also used in PCs (and other devices) to store critical low-level system information such as system setup data and the time and date, where the minimal current drain on a small lithium ion "CMOS battery" on a motherboard (for example) can keep this data safe for many years. | | | |
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