NMOS logic

N-type metal-oxide-semiconductor logic uses n-type field effect transistors (MOSFETs) to implement logic gates and other digital circuits. These nMOS transistors operate by creating an inversion layer in a p-type transistor body. This inversion layer, called the n-channel, can conduct electrons between n-type "source" and "drain" terminals. The n-channel is created by applying voltage to the third terminal, called the gate. Like other MOSFETs, nMOS transistors have four modes of operation: cut-off (or subthreshold), triode, saturation (sometimes called active), and velocity saturation.

MOS stands for metal-oxide-semiconductor, reflecting the way MOS-transistors were originally constructed, predominantly before the 1970s, with gates of metal, typically aluminium. Since around 1970, however, most MOS circuits have used self aligned gates made of polycrystalline silicon. These silicon gates are still used in most types of MOSFET based integrated circuits, although metal gates (Al or Cu) started to reappear in the early 2000s for certain types of high speed circuits, such as high performance microprocessors.