Transistor devices in CMOS logic Which transistor type is the fundamental active device used to implement complementary MOS (CMOS) logic gates?

Introduction / Context:
CMOS stands for Complementary Metal-Oxide-Semiconductor and is the dominant logic technology in modern integrated circuits. The specific transistor device at its core determines switching behavior, input impedance, and power characteristics.

Given Data / Assumptions:

• CMOS logic uses complementary pairs of transistors.
• The options include generic and specific transistor categories.

Concept / Approach:

CMOS is built from MOSFETs—specifically n-channel MOSFETs (NMOS) and p-channel MOSFETs (PMOS) arranged in complementary networks. While “FET” is a broader term that includes JFETs and MOSFETs, CMOS specifically relies on MOSFET devices with insulated gates (oxide), providing extremely high input impedance and very low static power consumption.

Step-by-Step Solution:

Verification / Alternative check:

Process technology nodes, SPICE models, and CMOS gate schematics confirm NMOS/PMOS MOSFET transistors form the pull-down and pull-up networks, respectively.

Why Other Options Are Wrong:

• FET: too generic; CMOS specifically uses MOSFETs.
• Bipolar: used in TTL/ECL, not CMOS logic cores.
• Unijunction: used in timing/trigger circuits, not logic gate cores.

Common Pitfalls:

• Answering “FET” because it is technically true that MOSFETs are FETs; the precise correct term here is MOSFET.

Final Answer:

MOSFET