Complementary metal-oxide-semiconductor (CMOS)

Complementary metal-oxide-semiconductor (CMOS) or-metal-oxide semiconductor complementary, is a major type of integrated circuit. CMOS technology used in microprocessors, micro controllers, static RAM, and other digital logic circuits. CMOS technology is also used in many analog circuits, such as image sensor, data converter, and trimancar integrated for various types of communication. Frank Wanlass successfully patented CMOS in 1967 (U.S. Patent 3,356,858).

CMOS is also often called complementary-symmetry metal-oxide-semiconductor or COSMOS (metal-oxide-semiconductor complementary-symmetry). Said complementary-symmetry refers to the fact that usually the CMOS-based digital design using complementary and symmetrical pairs of p-type semiconductor MOSFET and n-type semiconductors for logic functions.

Two important characteristics of CMOS is the high immunity he sighed and low static power consumption. Power is only drawn when the transistors in the CMOS switch between the conditions of life and death. As a result, CMOS devices do not generate heat as much as any other logic circuits, such as transistor-transistor logic (TTL) or NMOS logic, which only uses the n-type devices without p-type. CMOS also allows chips with high density logic made​​.

The phrase "metal-oxide-semiconductor" or semiconductor-metal-oxide is an appellation on the physical structure of some field-effect transistor, a gate electrode located above the metal insulator metal oxide, which is also located above the semiconductor material. Aluminum was first used, but is now used polysilicon material. Another metal gate is made over the arrival of high permittivity dielectric material in CMOS manufacturing process, as announced by IBM and Intel for the 45 nanometer node and smaller

"CMOS"refers to a particular digital circuit design, and the processes used to implement these circuits in the integrated circuit. CMOS Circuit waste less power when static, and allows the placement circuit that is more dense than other technologies that have the same function. When this advantage becomes more desirable, CMOS processes and variants dominates modern integrated digital circuits.

CMOS circuits using a combination of n-type MOSFET and p-type to construct logic gates and digital circuits found in computers, communications equipment, and signal processing equipment. Although CMOS logic can be built from separate components (as in the beginner project), usually CMOS products are integrated circuits composed of millions of transistors on a silicon area of ​​between 0.1 to 4 centimeters square. Devices are usually referred to as chips, while for the industry is also called a die (singular) or dice (plural).

CMOS designed so that all the PMOS transistors must have the input of the voltage source or from other PMOS transistor. Same thing, all NMOS transistors have to have input from the ground or other NMOS transistor. The composition of the PMOS transistor cause a low resistance when low voltage is applied to it, and high resistance when high voltage is applied. On the other hand, the composition of the NMOS transistor resulting high resistance when low voltage is applied to it, and low resistance when high voltage is applied.

The picture on the left shows what happens when an insert is connected to a PMOS transistor and NMOS transistors. When input A low voltage, NMOS transistors have a high resistance which prevents the voltage to leak to ground, while PMOS transistors have low resistance to allow the source voltage to move toward the output voltage through a PMOS transistor. The output should show a high voltage.

CMOS logic waste less power than NMOS logic because CMOS only a waste of power only when switching ("dynamic power"). In modern nanometer process in 1990, switching the output requires time 120 pikosekon, and repeated every ten nanosekon. NMOS logic wasting power when output is low ("static power"), because there is a path from Vdd to VSS through resistor load and the n-type network.

CMOS circuits power waste by filling out the wild when switching capacity. Moving charge is multiplication of wild capacity with changes in voltage. Multiply by the switching frequency to obtain borosan flow, and multiply by the voltage again to get borosan power characteristics of CMOS devices P = CV2f.

A borosan other resources found in the 1990s when the cable on the chip becomes longer and thinner. CMOS gates at the end of the cable receives the input transition is slow. In the midst of transition entries, all either NMOS or PMOS transistor to temporarily live together, and current flows directly from Vdd to VSS. Power used is called crowbar power. Careful design which avoids the driving wire is too long to reduce this borosan, and now crowbar power is always lower than the switching power.

Both NMOS or PMOS transistors have gate-source withstand voltage. Design of CMOS operating at supply voltages much higher than the voltage-resistant (more than 5 V Vdd, and Vth for NMOS and PMOS transistor is 700 mV).

To accelerate the design, manufacturers switched to gate material that has a lower withstand voltage. A modern NMOS transistors with Vth of 200 mV has a significant current leakage pratahan. Design is trying to optimize the manufacturing process to borosan minimum power during the operation have been pressing the Vth so that leakage currents approximately equal to the power switching. As a result, the devices are a waste of resources although there is no switching. Leakage power reduction using new material and system design is critical to sustaining scaling of CMOS. Manufacturing saw the introduction of high permittivity dielectrics to overcome the leakage current on the gate by replacing silicon dioxide with a material that has a higher permittivity.

Besides the use of digital, the CMOS technology is also used for analog use. An example is a CMOS op-amp IC. CMOS technology is also often used for radio frequency usage. Indeed, CMOS technology is also used for mixed signal integrated circuits (analog + digital).