Electronics: CMOS Technology and MOSFET

CMOS Technology

• CMOS technology is used in developing microprocessors, microcontrollers, and digital logic circuits.
• N-well is formed by diffusion.

CMOS Characteristics

• CMOS has high noise margin and high packing density.
• CMOS has low power dissipation.

MOSFET

• For a MOSFET with Vgs= 2V, Vtn =1v, Id=1mA, and λ =0.01v-1, its intrinsic gain is 200.
• In a MOSFET, Vgs is the voltage between the gate and source, and Vtn is the threshold voltage.

Inverter Circuits

• Inverters are essential for sequential circuits.
• In a basic inverter circuit, the source is connected to ground.
• In an inverter circuit, depletion mode transistors are used as load.
• In nMOS inverter configuration, depletion mode device is called as pull down.

VLSI Design Flow

• The design flow of VLSI system is: architecture design, market requirement, logic design, and HDL coding.

CMOS Fabrication

• In CMOS fabrication, nMOS and pMOS are integrated in the same substrate.
• P-well is created on an n-substrate.
• Photoresist layer is formed using light-sensitive polymer and is exposed to ultraviolet light.
• P-well doping concentration and depth will affect the threshold voltage.

CMOS Circuits

• CMOS circuits are good and better because they have low power consumption, less noise, and take up a small amount of space on a chip.
• The enhancement MOSFET is widely used because of its ease of fabrication.
• Mobility depends on the transverse electric field.
• For a symmetric CMOS inverter, (W/L)P = 2.5(W/L)N.

Poly Silicon

• Doping impurities is used to reduce the resistivity of poly silicon.

NMOS Inverter

• An nMOS inverter is represented by a specific circuit diagram.
• A CMOS inverter has four distinct modes of operation.

DIBL

• DIBL (Drain-Induced Barrier Lowering) has subthreshold conduction, gate leakage, and junction leakage as sources of leakage.