Complementary Metal Oxide


Complementary metal–oxide–semiconductor, also known as complementary-symmetry metal–oxide–semiconductor, is a type of metal–oxide–semiconductor field-effect transistor fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSFETs for logic functions. 

A complementary metal-oxide semiconductor (CMOS) consists of a pair of semiconductors connected to a common secondary voltage such that they operate in opposite (complementary) fashion. Thus, when one transistor is turned on, the other is turned off, and vice versa.

CMOS (short for complementary metal-oxide-semiconductor) is the term usually used to describe the small amount of memory on a computer MOTHERBOARD that stores the BIOS settings. Some of these BIOS SETTINGS include the system time and date, as well as HARDWARE settings.

A CMOS SENSOR is different—it’s used by digital cameras to convert images into digital data.

CMOS (pronounced see-moss) is sometimes referred to as Real-Time Clock (RTC)CMOS RAMNon-Volatile RAM (NVRAM)Non-Volatile BIOS memory, or complementary-symmetry metal-oxide-semiconductor (COS-MOS).

CMOS is also an abbreviation for other terms that are unrelated to what’s talked about on this page, like cellular management operation system and comparison mean opinion score.

Clearing CMOS

Most talk of CMOS involves clearing CMOS, which means to reset the BIOS settings to their default levels. This is a really easy task that’s a great troubleshooting step for many types of computer problems.

For example, maybe your computer is freezing up during the POST, in which case clearing the CMOS to reset the BIOS settings to factory default levels, might be the easiest solution.

Or maybe you need to clear CMOS to reset misconfigured BIOS settings to fix certain hardware-related error messages, such as CODE 29 errors. Other CMOS errors revolve around low battery voltage,CMO,S Checksum, battery failure, and read error.

CMOS sensors typically operate on a single low power supply or a few power supplies that can be derived from a single low power supply. Power supply requirements are typically achieved by use of only a few components and may also vary over a larger range without influencing the sensor performance. CMOS technology allows the on-chip integration of analogue and digital functionalities that require external components in case of CCDs. Examples are analogue-to-digital conversion, correlated double sampling, thresholding, signal processing, sequencing, etc. Furthermore, taking into account the limited number of available components, the cost of space qualification and long-term availability of such components, and the system power consumption, it is obvious that system dimensions and mass for CMOS-based systems can be significantly reduced. Payload size, power and mass have – in turn – a major impact on the cost of launch vehicles, and the economic viability of the mission. Thus, even if the cost of the CMOS detector or detector development may be higher in particular cases, the cost at system level can be significantly lower.

What are the characteristics of Complementary Metal Oxide Semiconductor CMOS )?

Two important characteristics of CMOS devices are high noise immunity and low static power consumption. Since one transistor of the MOSFET pair is always off, the series combination draws significant power only momentarily during switching between on and off states.

Advantages of CMOS

Following points summarize CMOS advantages over TTL and ECL:
➨The power per gate is 1 mW @ 1 MHz. This power consumption is less than TTL and CMOS.
➨The noise immunity is better than both TTL and ECL. The noise margin is about 40% of supply voltage.
➨Fanout (about > 50) is better than both TTL and ECL.
➨CMOS works satisfactorily over wide temperature range from -155 to 125 degree C.
➨It is compatible with 5V supply used in TTL circuits.
➨Nominal supply voltage ranges from 3V to 15V while TTL supports 5V.

Disadvantages of CMOS

Following points summarize CMOS disadvantages over TTL and ECL:
➨average propagation delay time (1 to 200 ns ) is worst compare to TTL and ECL logic families.

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