What is MOS k Parameter?

What is MOS k Parameter?

In a MOSFET (Metal–Oxide–Semiconductor Field-Effect Transistor), the k parameter (also written as k, k', or β) represents how strongly the transistor conducts current. It is basically a gain factor that links voltage to current.

Definition

k = (1/2) μ C_ox (W / L)

Where:

• μ = carrier mobility (electron or hole mobility)
• C_ox = oxide capacitance per unit area
• W = width of the channel
• L = length of the channel

Sometimes you may also see:

• k' = μ C_ox (process parameter)
• β = k = (1/2) k' (W / L)

In Drain Current Equation

I_D = k (V_GS - V_T)²

So:

• Larger k → more current for the same voltage
• Smaller k → less current

Summary

• A higher W/L ratio → bigger channel → higher current → larger k