PMOSFETs

A PMOSFET, or P-channel Metal-Oxide-Semiconductor Field-Effect Transistor, is a type of MOSFET where the majority charge carriers are holes. Unlike NMOSFETs which use electrons, PMOSFETs rely on the movement of positive charge carriers. The "P" in PMOS refers to the P-type semiconductor material used for the source and drain regions, which are heavily doped. The channel region between the source and drain is made of N-type silicon.

The operation of a PMOSFET is controlled by a gate voltage. The gate is insulated from the semiconductor by a thin layer of silicon dioxide, hence the "Oxide" in the name. When a negative voltage is applied to the gate relative to the source, it attracts holes from the P-type source and drain into the N-type channel region. This creates a conductive path for current to flow between the source and drain. A more negative gate-to-source voltage leads to a larger concentration of holes in the channel, resulting in lower resistance and higher current flow. Conversely, a less negative or positive gate voltage depletes the channel of holes, increasing resistance and reducing current.

PMOSFETs are typically used in complementary pairs with NMOSFETs in CMOS (Complementary Metal-Oxide-Semiconductor) logic circuits. This complementary configuration allows for very low static power consumption, as in a steady state, one transistor in the pair is always off, preventing direct current paths from the power supply to ground. They are commonly found in digital integrated circuits, power switching applications, and analog circuits.