N-MOS

electronics transistors mosfet

N-MOS

An N-MOS transistor is an N-channel MOSFET where the channel consists of electrons as majority carriers. It operates in enhancement mode: applying a positive gate-source voltage (where ) creates an inversion layer, forming a conducting channel between source and drain.

Structure

Substrate: p-type semiconductor (lightly doped). Source/Drain: Heavily doped n+ regions diffused into the substrate. Gate: Metal or polysilicon electrode separated from the substrate by a thin oxide layer. Channel: Forms beneath the gate when (positive threshold).

Operation

Off State (): No conducting channel exists; drain current . The transistor acts as an open switch.

On State (): Positive gate voltage attracts electrons to the surface, creating an n-type inversion layer (channel) connecting source to drain. Current flows from drain (higher potential) to source (lower potential).

Example

Consider an N-MOS with :

Condition		State
,		Off
,		On

When used as a low-side switch: source connected to ground (), gate driven high () to turn on, allowing current to flow from the load through the drain to ground.