MOSFET Saturation Drain Current

\[I_D=\frac{k}{2}(V_{GS}-V_{th})^2\]

Variables

Iddrain current (A)

kMOSFET transconductance parameter (A/V²)

Vgsgate-source voltage (V)

Vththreshold voltage (V)

Description

What is this formula?

The MOSFET Saturation Drain Current formula calculates the drain current of a MOSFET operating in the saturation region. This is one of the most important operating regions for analog amplification.

When to use it

Use this formula when analyzing or designing MOSFET amplifiers, analog integrated circuits, switching electronics, or transistor bias networks.

Example

An NMOS transistor has a transconductance parameter of 0.5 A/V², a threshold voltage of 2 V, and a gate-source voltage of 5 V.

Given:

k = 0.5 A/V²

Vgs = 5 V

Vth = 2 V

Formula:

Id = (k/2)(Vgs - Vth)^2

Substitution:

Id = (0.5/2)(5 - 2)^2

Result:

Id = 2.25 A

The MOSFET drain current is 2.25 A.

Applications

MOSFET amplifiers, CMOS circuits, analog integrated circuits, switching power supplies, electronic drivers, and semiconductor electronics.