What is CMOS? Working, Applications, & Types | CMOS Full Form

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What is CMOS Technology?

CMOS stands for “Complementary Metal Oxide Semiconductor“; it is a prevalent technology for manufacturing integrated circuits, including microprocessors, microcontrollers, memory chips, and other digital logic circuits. It enables with using of both NMOS (N-type Metal Oxide Semiconductor) and PMOS (P-type Metal Oxide Semiconductor) transistors to realize various logic functions.

CMOS technology

The structure of CMOS transistors consists of the NMOS transistor inverted on the top of the PMOS transistor, with the substrate being P-type and three N++ regions. CMOS technology provides many benefits including high noise immunity, low static power consumption, and the ability to operate over the large range of power supply voltages.

CMOS Tutorial Headlines:

In this section, we will show you all headlines about this entire article; you can check them as your choice; below shown all:

  1. What is CMOS Technology?
  2. History of CMOS Technology
  3. Working Principle CMOS Circuit
  4. How to Reset CMOS Battery?
  5. How to CMOS and BIOS Work Together?
  6. Difference Between CMOS and BIOS
  7. CMOS Applications & Use Cases
  8. Advantages of CMOS
  9. Disadvantages of CMOS
  10. FAQs (Frequently Asked Questions)
  • What does CMOS stand for?
  • What is CMOS technology used for?
  • What is CMOS battery?
  • What is the role of NMOS and PMOS transistors in CMOS technology?
  • How is a CMOS NAND gate constructed?
  • How is CMOS technology manufactured?

Let’s Get Started!!

History of CMOS Technology

Here, we will show you some interested points about the history of CMOS (Complementary Metal Oxide Semiconductor) technology:

1960s: CMOS (Complementary Metal-Oxide-Semiconductor) technology was first conceptualized in the 1960s.

1963: Frank Wanlass, an engineer at Fairchild Semiconductor, introduced the concept of CMOS technology.

1970s: Researchers at RCA and IBM further developed CMOS technology during the 1970s, making significant advancements.

1972: RCA introduced the first CMOS IC (Integrated Circuit).

1980s: CMOS gained popularity due to its low power consumption compared to other technologies, making it suitable for portable devices.

1990s: CMOS technology became the dominant choice for semiconductor manufacturing, leading to the development of more powerful and energy-efficient microprocessors.

2010s: CMOS technology continued to evolve, enabling the production of smaller and more energy-efficient electronic devices, including smartphones, tablets, and wearables.

Present: CMOS is getting to remain the dominant technology for manufacturing digital integrated circuits, with forming the backbone of modern electronic devices and computing systems.

Working Principle CMOS Circuit

Here is a brief explanation of the working principle of CMOS along with a simple diagram:

working of CMOS


  • MOSFETs are the building blocks of CMOS circuits. There are two types: n-type (NMOS) and p-type (PMOS).
  • NMOS transistors are constructed with n-type semiconductor material (source and drain), and PMOS transistors use p-type semiconductor material.
  • A MOSFET has three terminals: Gate (G), Source (S), and Drain (D).

Basic CMOS Inverter

  • The fundamental building block of CMOS is the inverter, which consists of one NMOS and one PMOS transistor connected in series.
  • When the input signal (Vin) is high, the NMOS transistor conducts, creating a low resistance path to ground (GND).
  • When the input signal is low, the PMOS transistor conducts, connecting the output to the power supply voltage (VDD).

Inverter Operation

  • When Vin is high, the NMOS is ON, and the PMOS is OFF. The output (Vout) is pulled low to GND.
  • When Vin is low, the NMOS is OFF, and the PMOS is ON. The output is pulled high to VDD.

Inverter Operation

  • If Vin is high, the NMOS is ON, providing a low-resistance path to GND. The output is pulled low (logic 0).
  • If Vin is low, the PMOS is ON, connecting the output to VDD. The output is pulled high (logic 1).

This basic CMOS inverter operation forms the basis for constructing more complex digital circuits, such as NAND gates, NOR gates, flip-flops, and other logical building blocks.

CMOS Logic Gates

Complementary Metal-Oxide-Semiconductor (CMOS) logic gates are the building blocks of digital integrated circuits. Here are some commonly used CMOS logic gates:

CMOS Inverter

  • The basic CMOS inverter is constructed using one NMOS transistor and one PMOS transistor connected in series.
  • When the input is high, the NMOS conducts (low impedance path to ground), pulling the output low.
  • When the input is low, the PMOS conducts (low impedance path to VDD), pulling the output high.


CMOS nand gate

  • A CMOS NAND gate is created by combining multiple transistors in series and parallel.
  • It has multiple inputs (A, B, …) and produces the logical AND of those inputs.

Truth Table for Two-input NAND Gate






CMOS nor gate

A CMOS NOR gate is constructed similarly to a NAND gate, but with transistors arranged differently to produce the logical NOR operation.

Truth Table for Two-input NOR Gate







CMOS XOR (exclusive OR) and XNOR (exclusive NOR) gates can be implemented using a combination of inverters, NAND gates, and NOR gates.

How to Reset CMOS Battery?

To reset the CMOS (Complementary Metal-Oxide-Semiconductor) settings on your computer, you can follow these general steps:

Power Off: Shut down your computer and turn off the power supply.

Disconnect Power: Unplug the power cord from the power outlet to ensure no electrical current is flowing through the system.

Open the Case: Open the computer case to access the motherboard.

Locate the CMOS Battery: Identify the CMOS battery on the motherboard. It is a coin-cell battery (usually a CR2032) that provides power to the CMOS chip to retain settings.

Remove the CMOS Battery: Carefully remove the CMOS battery from its socket. You may need a small flat-head screwdriver to gently pry it out.

Wait for a Few Minutes: Allow the system to remain without the CMOS battery for a few minutes. This allows the residual charge to dissipate, effectively resetting the CMOS settings.

Reinsert the CMOS Battery: Put the CMOS battery back into its socket, ensuring it is properly seated.

Close the Case: Close the computer case.

Reconnect Power: Plug in the power cord and turn on the power supply.

Power On: Start your computer. The CMOS settings should now be reset to their default values.

How to CMOS and BIOS Work Together?

The BIOS and CMOS work together to keep managing the computer’s start up process. The BIOS, stored in non-volatile memory on the motherboard, initializes hardware components during boot.

It then accesses configuration data stored in the CMOS memory, a volatile chip powered by a small battery, to retrieve system settings such as date, time, and hardware parameters.

The CMOS stores this information even when the computer is powered off. The collaboration between BIOS and CMOS ensures proper hardware initialization and system configuration, facilitating a smooth and consistent boot sequence for the computer system.

Difference Between CMOS and BIOS





CMOS technology pertains to the type of semiconductor manufacturing process. CMOS memory specifically refers to the volatile memory used for system configuration data storage.BIOS is firmware, a set of instructions stored on a chip, responsible for initializing hardware during the boot process


Usually found in the SouthbridgeUsually found in separate chipset called EPROM or Flash memory in the motherboard


Stores BIOS configuration settings

Initializes hardware during the booting process and provides runtime services for the operating system




Can be changed through CMOS setup

Can be upgraded by


CMOS Applications & Use Cases

CMOS (Complementary Metal-Oxide-Semiconductor) technology is widely used in various electronic devices. Some of the key applications include:

Digital Integrated Circuits

CMOS is extensively used in digital integrated circuits (ICs) such as microprocessors, microcontrollers, memory chips, and digital signal processors (DSPs).

Analog Integrated Circuits

CMOS is also used in analog integrated circuits, including operational amplifiers, voltage regulators, and analog-to-digital converters (ADCs). Advancements in CMOS technology have enhancement the performance of analog circuits that is making them more energy-efficient.


Radio-Frequency Identification (RFID) tags often use CMOS technology for their integrated circuits. CMOS RFID tags are cost-effective, small in size, and can operate with minimal power.

Micro Electromechanical Systems (MEMS)

CMOS is employed in the fabrication of MEMS devices, which combine mechanical and electronic components on a single chip. For examples are accelerometers, gyroscopes, and pressure sensors.

Biomedical Devices

CMOS technology is utilized in various biomedical applications, including biosensors and medical imaging devices. CMOS-based sensors can be used for detecting biological substances and monitoring physiological parameters.

Communication Systems

CMOS technology is commonly used in communication systems, including wireless transceivers and network equipment. Its low power consumption is particularly advantageous in battery-operated devices.

Smart Cards

CMOS technology is used in the manufacturing of smart cards for applications like credit cards, identification cards, and access control cards. It facilitates the secure and power-efficient solution for using of embedded systems.

Digital Audio Processing

CMOS is used in digital audio processing applications, including codecs and digital audio players. It enables the integration of complex signal processing functions while maintaining energy efficiency.

Digital Clocks and Timing Circuits

CMOS is widely used in digital clock circuits and timing generators due to its low power consumption and stability.

Advantages of CMOS

Here are the advantages & benefits of CMOS technology:

Also Read: CMOS Inverter with Working Operations and Applications

Low Power Consumption: CMOS circuits consume very low power, making them suitable for battery-powered devices and energy-efficient applications.

Complementary Design: CMOS uses complementary logic design with both n-type and p-type transistors, reducing static power consumption and improving noise margins.

High Integration Density: CMOS technology allows for the integration of a large number of transistors on a single chip, enabling the development of complex and highly integrated circuits.

Reduced Heat Generation: Due to low power consumption, CMOS circuits generate less heat compared to other technologies, contributing to improved reliability and longer device lifespan.

Wide Operating Voltage Range: CMOS devices can operate over a wide range of supply voltages, providing flexibility in design and compatibility with different power sources.

Scalability: CMOS technology is scalable, allowing for the development of smaller and more efficient devices as technology advances.

High Noise Immunity: Complementary design and low power supply voltage contribute to high noise immunity in CMOS circuits, making them robust in noisy environments.

Low Manufacturing Cost: CMOS fabrication processes are well-established and widely used, leading to cost-effective production of CMOS-based devices.

Radiation Resistance: CMOS circuits are generally less susceptible to radiation-induced errors compared to other technologies, making them suitable for use in space applications.

Reduced Leakage Current: Advancements in CMOS technology have led to lower leakage currents, enhancing energy efficiency and battery life in portable devices.

High Speed: CMOS circuits can operate at high speeds, making them suitable for applications requiring fast data processing and high-frequency signals.

Disadvantages of CMOS

The disadvantages of CMOS (Complementary Metal Oxide Semiconductor) technology are relatively few, but they include:

Limited Analog Performance: While CMOS is widely used in digital applications, its analog performance may not be as high as some other technologies, especially in terms of linearity and precision.

Susceptible to Process Variations: CMOS devices are sensitive to process variations, which can result in performance variations across different manufactured chips.

Reduced Speed at Low Power: In some cases, reducing power consumption in CMOS circuits can lead to a reduction in processing speed, creating a trade-off between power efficiency and performance.

Latch-Up Phenomenon: CMOS circuits are susceptible to latch-up, a condition where parasitic structures cause unintended short circuits. Special care must be taken in the design to prevent latch-up.

Limited Power Supply Voltage Range: While CMOS devices are designed to operate over a range of voltages, extreme variations in the power supply voltage can affect their performance and reliability.

Issues with Radiation Sensitivity: Despite having relatively good radiation resistance, CMOS devices can still be sensitive to high levels of radiation, which can be a concern in certain applications such as space exploration.

Increased Sub threshold Leakage: As the size of CMOS transistors decreases, sub-threshold leakage currents can become more significant, leading to increased power consumption in standby modes.

Complex Clocking and Synchronization: In high-performance applications, managing clocking and synchronization in CMOS circuits can become complex, requiring careful design to avoid issues such as clock skew.

FAQs (Frequently Asked Questions)

What does CMOS stand for?

CMOS stands for Complementary Metal-Oxide-Semiconductor.

What is CMOS technology used for?

CMOS technology is commonly going to use for constructing integrated circuits, such as memory chips, microprocessors, and other digital logic circuits in electronic devices.

What is CMOS battery?

CMOS battery often a small coin cell, powers the CMOS (Complementary Metal-Oxide-Semiconductor) chip on a computer motherboard. It preserves system settings, including date and time, when the main power is turned off, ensuring data integrity and system functionality.

What is the role of NMOS and PMOS transistors in CMOS technology?

NMOS (n-type) and PMOS (p-type) transistors are used in CMOS technology to create complementary pairs. NMOS conducts when the input is high, while PMOS conducts when the input is low, enabling efficient digital logic design.

How is a CMOS NAND gate constructed?

A CMOS NAND gate is constructed using both NMOS and PMOS transistors. The transistors are arranged in such a way that the output is low (logic 0) only when both inputs are high (logic 1).

How is CMOS technology manufactured?

CMOS technology is manufactured using semiconductor fabrication processes. This involves creating n-type and p-type regions on a silicon substrate, forming transistors, interconnecting them, and adding additional layers to create complex integrated circuits.

Final Words

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Also Read: What is BIOS? Types, Uses and its Functions

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