Glossary / Semiconductors
CMOS
A circuit style that pairs the two opposite types of MOS transistor. Current flows only at the moment of switching, so power consumption is tiny.
In 1963 Frank Wanlass and Chih-Tang Sah at Fairchild combined an n-type MOS transistor, which conducts with electrons, and a p-type, which conducts with holes, so that one of them is always off. At rest almost no current flows — the "nanowatt logic" of their paper's title[1].
That frugality is what keeps billions of transistors on one chip within a manageable heat budget. Almost every digital circuit today, from phones to supercomputers, is CMOS.
Related terms
- MOS transistorA transistor built from a metal electrode, an oxide layer and a semiconductor, in which a voltage on the electrode alone opens and closes the channel. Most of today's chips are made of these.
- Dennard scalingThe design rule that shrinking a transistor's dimensions and voltage by the same factor makes it faster and more efficient while keeping heat per unit area constant.
- Integrated circuitA circuit in which transistors and other components, together with the wiring between them, are all built into a single piece of semiconductor — a chip.