P-MOS

electronics transistors mosfet

P-MOS

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

Structure

Substrate: n-type semiconductor (lightly doped). Source/Drain: Heavily doped p+ 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 (negative threshold).

Operation

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

On State (): Negative gate voltage attracts holes to the surface, creating a p-type inversion layer (channel) connecting source to drain. Current flows from source (higher potential) to drain (lower potential).

Example

Consider a P-MOS with :

Condition		State
,		Off
,		On

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