What is the definition of CMOS

CMOS definition & explanation of terms

Interested and electronics enthusiastic users who own a computer have probably already become familiar with the term CMOS. CMOS is an abbreviation for Complementary Metal Oxide Semiconductor and describes a high-quality semiconductor element that consists of a conductive metal and an oxide component. In the context of semiconductor components, the CMOS has established itself as the basic operating element for an electronic system for data processing and is included in every computer-aided functional unit.


The job of the CMOS is to transmit, store and process both digital and analog data. The CMOS is particularly suitable for integration in microcircuits. In this context, the CMOS serves as a storage basis for the data required to configure a computer system. These are located in the BIOS and are stored in the CMOS RAM memory.

This can only be done if the CMOS RAM is equipped with its own power supply, which is available in the computer as an independent accumulator or battery. The CMOS first saves the password that the user enters when he wants to work with his computer. If the CMOS is cut off from the power supply due to the interruption of the contact between the computer and the battery, the password and all configuration data stored in the CMOS are automatically deleted after a certain period of time.

The term semiconductor comes from the company in which this semiconductor was invented and built. In addition, the Complementary Metal Oxide Semiconductor is an innovative semiconductor technology that is used to manufacture the microtransistors.

CMOS components

Different components have proven themselves through their use within the technology of the CMOS. The CMOS itself is a field effect transistor and is only a few millimeters in size. A HCT CMOS is based on the synchronization of a so-called CMOS transistor structure to different levels of the input voltage, which can be observed in the TTL circuit.

Identifying the HCT CMOS is a technical property known as pin compatibility. The Bi CMOS is a component that is based on the similar functionality of field effect transistors in combination with bipolar transistors. In general, all CMOS types represent the prerequisite that several channels can be integrated on one chip. In addition to these advantages, the CMOS is characterized by an astonishingly low energy consumption and is considered to be extremely durable.

Importance of CMOS

The CMOS is often referred to as BIOS CMOS in the context of a motherboard or computer system. When a computer is disconnected from the mains, the power supply to the motherboard is also switched off. Logically, this would have to result in the deletion of all data that is not on a magnetic storage medium. This is not the case with CMOS. There are two reasons. On the one hand, the CMOS can store system-relevant information independently of the power supply, which includes other important configuration parameters in addition to the time, the password and the date.

On the other hand, the CMOS is constantly under voltage, because an extremely powerful and long-lasting battery supplies the semiconductor with electricity. This is the prerequisite for system-relevant data such as various information about the hard disk and other electronic components to be saved and preserved despite the power interruption. The CMOS is one of the so-called slow memory modules and is therefore not written to directly by some operating systems. They store their configuration parameters and the information content of the CMOS via a memory shadow, a copying process in the RAM.

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