CMOS stands for

Question

CMOS stands for

Examoogle · Accepted Answer

Complementary MOS

Explanation: CMOS stands for Complementary Metal-Oxide-Semiconductor. It is a dominant semiconductor technology used to construct integrated circuits, including microprocessors, microcontrollers, and digital logic circuits.

Working Principle: The principle relies on the complementary arrangement of PMOS and NMOS transistors. In a CMOS inverter, when the input is high, the NMOS transistor conducts and pulls the output low; when the input is low, the PMOS transistor conducts and pulls the output high. This configuration ensures that under static conditions, one transistor is always 'OFF', resulting in near-zero power dissipation.

Key Formulas: $P_{dynamic} = \alpha C_L V_{DD}^2 f$; $P_{static} = I_{leakage} V_{DD}$

Key Points: CMOS circuits are characterized by high noise immunity and low static power dissipation.; The 'Complementary' aspect refers to the use of both p-type and n-type enhancement-mode MOSFETs.; CMOS is the foundation of almost all modern VLSI (Very Large Scale Integration) designs.; It replaced NMOS logic due to significantly lower power consumption in the 1980s.

Advantages: Extremely low power consumption during steady state; High noise immunity; High packing density on silicon wafers

Disadvantages: More complex fabrication process compared to NMOS; Susceptible to latch-up effect due to parasitic thyristor structures; Performance degrades at very high temperatures

Applications: Digital processors and microcontrollers; Static RAM (SRAM) and imaging sensors; Data converters and communication ICs

Additional Info: Option A is incorrect as 'Common MOS' is not a technical term.. Option B refers to a specific logic style (Active-load logic), not the expansion of CMOS.. Option C is a description of the composition but not the definition of the acronym.

Answer: D is correct — CMOS stands for Complementary Metal-Oxide-Semiconductor, describing the use of complementary PMOS and NMOS pairs in logic design.

Exam Tip: Always remember that in CMOS, the 'Complementary' nature is what prevents direct path current from $V_{DD}$ to Ground, which is the primary reason it is preferred for battery-operated devices.

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