what is CMOS?

Question

full description of CMOS

Answer 1

complementary metal oxide semiconductor

CMOS
(Complementary Metal Oxide Semiconductor) Pronounced "

c
-moss." The most widely used integrated circuit design. It is found in almost every electronic product from handheld devices to mainframes. CMOS uses PMOS and NMOS transistors wired together in a balanced fashion that causes less power to be used than NMOS or PMOS transistors by themselves. The first transistors were bipolar, which are still used when higher power is required. CMOS and bipolar are also used in combination for many applications. See MOSFET, FET and bipolar. See also CMOS memory.

A Note from the Author
Years ago, we had a kitten at the beach that we named CMOS. When we introduced the cute feline to people while the surf was slapping the sand, everyone thought it was such an appropriate name for a beach cat. "Sea Moss." Of course! However, when we told them her name stood for "complementary metal oxide semiconductor," they didn't come around much any more.

CMOS ("see-moss"), which stands for complementary metal-oxide semiconductor, is a major class of integrated circuits. CMOS chips include microprocessor, microcontroller, static RAM, and other digital logic circuits. The central characteristic of the technology is that it only uses significant power when its transistors are switching between on and off states. Consequently, CMOS devices use little power and do not produce as much heat as other forms of logic. CMOS also allows a high density of logic functions on a chip.

The word "complementary" refers to the fact that the design uses pairs of transistors for logic functions, only one of which is switched on at any time.

The phrase "metal-oxide-semiconductor" is a reference to the nature of the fabrication process originally used to build CMOS chips. That process created field effect transistors having a metal gate electrode placed on top of an oxide insulator, which in turn is on top of a semiconductor material. Instead of metal, today the gate electrodes are almost always made from a different material, polysilicon, but the name CMOS nevertheless continues to be used for the modern descendants of the original process. (See also MOSFET.)

A chip with a large number of CMOS transistors packed tightly together is sometimes known as CHMOS (for "Complementary High-density metal-oxide-semiconductor").

The combination of MEMS sensors with digital signal processing on one single CMOS chip is sometimes known an CMOSens.

Development history
CMOS circuits were invented in 1963 by Frank Wanlass at Fairchild Semiconductor. The first CMOS integrated circuits were made by RCA in 1968 by a group led by Albert Medwin. Originally a low-power but slow alternative to TTL, CMOS found early adopters in the watch industry and in other fields where battery life was more important than speed. Some twenty-five years later, CMOS has become the predominant technology in digital integrated circuits. This is essentially because area occupation, operating speed, energy efficiency and manufacturing costs have benefited and continue to benefit from the geometric downsizing that comes with every new generation of semiconductor manufacturing processes. In addition, the simplicity and comparatively low power dissipation of CMOS circuits have allowed for integration densities not possible on the basis of bipolar junction transistors.

Standard discrete CMOS logic functions were originally available only in the 4000 series of logic integrated circuits. Later many functions in the 7400 series began to be fabricated in CMOS, NMOS, BiCMOS or another variant.

Early CMOS circuits were very susceptible to damage from electrostatic discharge (ESD). Subsequent generations were thus equipped with sophisticated protection circuitry that helps absorb electric charges with no damage to the fragile gate oxides and PN-junctions. Still, antistatic handling precautions for semiconductor devices continue to be followed to prevent excessive energies from building up. Manufacturers recommend using antistatic precautions when adding a memory module to a computer, for instance.

On the other hand, early generations such as the 4000 series that used aluminum as a gate material were extremely tolerant of supply voltage variations and operated anywhere from 3 to 18 volts DC. For many years, CMOS logic was designed to operate from the then industry-standard of 5 V imposed by TTL. By 1990, lower power dissipation was usually more important than easy interfacing to TTL, and CMOS voltage supplies began to drop along with the geometric dimensions of the transistors. Lower voltage supplies not only saved power, but allowed thinner, higher performance gate insulators to be used. Some modern CMOS circuits operate from voltages below one volt.

In the early fabrication processes, the gate electrode was made of aluminum. Later CMOS processes switched to polycrystalline silicon ("polysilicon"), which can better tolerate the high temperatures used to anneal the silicon after ion implantation. This means that the gate can be put on early in the process and then used directly as an implant mask producing a self aligned gate (gates that are not self aligned require overlap which increases device size and stray capacitance). As of 2004 there is some research into using metal gates once again, but all commonly used processes have polysilicon gates. There is also a great deal of research going on to replace the silicon dioxide gate dielectric with a high-k dielectric material to combat increasing leakage currents.

Technical details
CMOS (complementary metal oxide semiconductor) refers to both a particular style of digital circuitry design, and the family of processes used to implement that circuitry on integrated circuits (chips). CMOS logic on a CMOS process dissipates less energy and is more dense than other implementations of the same functionality. As this advantage has grown and become more important, CMOS processes and variants have come to dominate, so that as of 2006 the vast majority of integrated circuit manufacturing by dollar volume is on CMOS processes.

Structure
CMOS logic uses a combination of p-type and n-type metal-oxide-semiconductor field effect transistors (MOSFETs) to implement logic gates and other digital circuits found in computers, telecommunications and signal processing equipment. Although CMOS logic can be implemented with discrete devices (for instance, in an introductory circuits class), typical commercial CMOS products are integrated circuits composed of millions (or hundreds of millions) of transistors of both types on a rectangular piece of silicon of between 0.1 and 4 square centimeters. These bits of silicon are commonly called chips, although within the industry they are also referred to as die, perhaps because they are the result of dicing (that is, cutting up) the circular silicon wafer which is the basic unit of semiconductor device fabrication.

In CMOS logic gates a collection of n-type MOSFETs is arranged in a pull-down network between the output and the lower-voltage power supply rail (often named Vss). Instead of the load resistor of NMOS logic gates, CMOS logic gates have a collection of p-type MOSFETs in a pull-up network between the output and the higher-voltage rail (often named Vdd). The p-type transistor network is complementary to the n-type transistor network, so that when the n-type is off, the p-type is on, and vice-versa.

CMOS logic dissipates less power than NMOS logic because CMOS dissipates power only when switching (dynamic power). On a typical ASIC in a modern 90 nanometer process, switching the output might take 120 picoseconds, and happen once every ten nanoseconds. NMOS logic dissipates power whenever the output is low (static power), because there is a current path from Vdd to Vss through the load resistor and the n-type network.

P-type MOSFETs are complementary to n-type because they turn on when their gate voltage goes sufficiently below their source voltage, and because they can pull the drain all the way to Vdd. Thus, if both a p-type and n-type transistor have their gates connected to the same input, the p-type MOSFET will be on when the n-type MOSFET is off, and vice-versa.

Answer 2

---Also known as a RTC/NVRAM or CMOS RAM, CMOS is short for Complementary Metal-Oxide Semiconductor. CMOS is an on-board semiconductor chip powered by a CMOS battery inside IBM compatible computers that stores information such as the system time and system settings for your computer. A CMOS is similar to the Apple Macintosh computer's PRAM.


that means that it stores the basic information to run your computer, even lower than XP and DOS. most name brand computers dont have a CMOS jumper, but most personal-built computers do. when you activate the jumper, it "kills" your entire computer and wipes out all of the basic info (like time, boot order, error beeps) and has sometimes been known to fix major boot-up problems of servers that would normally cost 10's of thousands of dollars to fix.

Answer 3

"CMOS" can also refer to nonvolatile memory of a personal computer; see Nonvolatile BIOS memory.
For the style guide sometimes called "CMOS" see The Chicago Manual of Style.

Static CMOS Inverter
Static CMOS Inverter

CMOS ("see-moss", IPA:['si.mɜs]), which stands for complementary metal-oxide semiconductor, is a major class of integrated circuits. CMOS chips include microprocessor, microcontroller, static RAM, and other digital logic circuits. The central characteristic of the technology is that it only uses significant power when its transistors are switching between on and off states. Consequently, CMOS devices use little power and do not produce as much heat as other forms of logic. CMOS also allows a high density of logic functions on a chip.

The word "complementary" refers to the fact that the design uses pairs of transistors for logic functions, only one of which is switched on at any time.

The phrase "metal-oxide-semiconductor" is a reference to the nature of the fabrication process originally used to build CMOS chips. That process created field effect transistors having a metal gate electrode placed on top of an oxide insulator, which in turn is on top of a semiconductor material. Instead of metal, today the gate electrodes are almost always made from a different material, polysilicon, but the name CMOS nevertheless continues to be used for the modern descendants of the original process. (See also MOSFET.)

A chip with a large number of CMOS transistors packed tightly together is sometimes known as CHMOS (for "Complementary High-density metal-oxide-semiconductor").

The combination of MEMS sensors with digital signal processors on one single CMOS chip is sometimes known an CMOSens.

Answer 4

Complementory Metal Oxide Semiconductor.

Answer 5

Complimentary Metal-Oxide Semiconductor.

It's where your computer's BIOS is stored.

Answer 6

complementary metal-oxide semiconductor

http://en.wikipedia.org/wiki/CMOS

Answer 7

Run it through a google search. You'll get blasted with tons of answers!

Answer 8

You're probably thinking of this:

http://en.wikipedia.org/wiki/Nonvolatile_BIOS_memory