CMOS

Complementary metal–oxide–semiconductor (CMOS) is a special way of making tiny parts called transistors that help computers and other gadgets work. It uses two types of transistors working together to create logic functions, which are the basic building blocks for digital circuits. Because of this clever design, CMOS has become the most common way to make computer chips, including the brains of computers microprocessors, memory chips memory chips, and many other important parts.

CMOS became popular in the 1980s because it uses less power and creates less heat than older technologies. This means we can pack lots of these tiny parts onto a single chip without them getting too warm. This ability to fit many parts into a small space helped make modern computers and gadgets possible. Even today, almost all computer chips are made using CMOS technology.

The idea for CMOS started with important discoveries in the 1940s, and it was first shown as a real technology in the 1960s. Over time, engineers have kept improving it, allowing them to make chips with incredibly small parts. CMOS isn’t just for computers; it’s also used in cameras, sensors, and many other electronic devices that need to be small, fast, and efficient.

History

Main article: History of the transistor

Further information: MOSFET and Transistor density

The idea of using pairs of transistors to create logic circuits was first suggested in 1953. Over the next few years, scientists and engineers worked on improving these ideas, creating new types of transistors and circuits.

By the 1960s, a new way to build transistors called CMOS was invented. This technology used two types of transistors working together. It wasn’t widely used at first, but it became very important because it used less power. In the 1970s, CMOS was used in small devices like calculators and watches. By the 1980s, CMOS became the main way to build computer chips, because it allowed for smaller, faster, and more efficient computers. Today, most modern chips use CMOS technology, though new methods are being developed to make even smaller and better chips.

Technical details

Further information: Semiconductor manufacturing processes

CMOS is a special way to build digital circuits using tiny parts called transistors. It uses two types of transistors together, which helps save energy. Because of this, CMOS has become the most common way to make computer chips today. These chips can have billions of transistors packed onto a small piece of silicon, which is a material that helps control electricity.

CMOS circuits use a special mix of transistors to create the basic building blocks of computers and other digital devices. This method uses less power than older ways of building circuits, making modern electronics more efficient and smaller.

Inversion

CMOS circuits are built using two types of transistors: PMOS and NMOS. These transistors work together in a special way. When a low voltage is applied, the PMOS transistor allows current to flow, while the NMOS transistor blocks it. When a high voltage is applied, the NMOS transistor allows current to flow, but the PMOS transistor blocks it. This setup helps save power because the transistors only use energy when they are switching between states.

The output of a CMOS circuit is always the opposite of its input. If the input is low, the output is high, and if the input is high, the output is low. This makes CMOS circuits very reliable and able to handle many connections without losing information. Because of this design, CMOS is used in most modern electronic devices, from computers to simple chips.

Power: switching and leakage

CMOS logic uses less power than older types of circuits because it only uses power when it is switching on or off. When a CMOS circuit is not switching, it uses almost no power. As chips have gotten smaller, using less power has become very important.

Power use in CMOS comes from two main sources. The first is when the circuit is switching, which uses power to charge up tiny parts of the circuit. The second is a small amount of power that leaks even when the circuit is not doing anything. Engineers work hard to reduce this leakage so that chips can stay cool and work well.

Input protection

In CMOS technology, certain parts of the design can accidentally turn on if there are unusual signals, like sudden electric shocks or reflections from wires. This can hurt or break the device. To stop this, special parts called clamp diodes are added to the circuits. These diodes help protect the device by controlling how much current can flow through it, as described in the manufacturer's instructions.

Analog CMOS

CMOS technology is not just for digital devices; it is also used in analog applications. For example, there are special chips called CMOS operational amplifier that can be bought. It can also be used to make tiny switches called transmission gates that can control the flow of signals instead of using bigger parts called relays. CMOS is even used in circuits that work with radio waves, all the way up to very high frequencies, especially when these circuits need to do both analog and digital tasks at the same time, known as mixed-signal applications.

RF CMOS

Main article: RF CMOS

RF CMOS refers to special circuits that use CMOS technology to work with radio frequencies. These circuits are used in many wireless communication devices. This type of technology was developed in the late 1980s, and it changed how radio parts were made. Instead of using separate parts, RF CMOS uses tiny chips to create the entire radio, making devices smaller, cheaper, and using less power. This helped make wireless communication easy to use anywhere, leading to the growth of wireless technology.

Today, RF CMOS is used in almost all wireless devices and phones. It helps send and receive signals for many things, like satellite systems such as GPS, Bluetooth, Wi-Fi, near-field communication, mobile networks like 3G and 4G, terrestrial broadcast, and even in cars for radar systems. Many companies make RF CMOS chips for products such as cordless phones, Wi-Fi devices, Bluetooth, and wireless networks. RF CMOS plays a big role in making modern wireless communication possible, including networks and mobile devices.

Temperature range

Conventional CMOS devices can work in temperatures from -55 °C to +125 °C.

There were signs in 2008 that silicon CMOS might work as low as -233 °C (40 K). Devices have worked near 40 K using special cooling methods. Silicon carbide CMOS devices have also been tested at very high temperatures of 500 °C.

Phenom II liquid nitrogen liquid helium Silicon carbide

Single-electron MOS transistors

Very tiny transistors, about as small as 20 nanometers wide, can work at extremely cold temperatures, from about -269 °C to -258 °C. At these temperatures, the transistors behave in a special way because they let electrons flow one at a time. The number of electrons that can pass through the transistor depends on the voltage applied to a part called the gate, and this can be controlled to allow zero, one, or many electrons to pass.