Complimentary Metal Oxide Silicon, or, more recently, Complimentary Metal Oxide Semiconductor. This is the name for a technology often used to produce logic gates/circuits/functions in silicon. It is characterized by high input impedance* and low power consumption. It has many other advantages as well.

It is the primary technology used in the construction of CPUs, and is also used for a series of discrete logic chips called the 4xxx series (say: "four thousand series").

Recently, the well known TTL series (74xxx series) have been replaced with a series of CMOS chips. These have the same functions as their respective TTL series chips, but they are constructed with CMOS. They are referred to as the 74HCxxx series chips, where HC signifies that they are implemented in "High-speed CMOS."


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*input impedance Statically (when the input signal is not in transition from one state to another) the input is practically an open circuit (10¹², or about 1 trillion ohms). Dynamically (i.e., when transitioning), gate capacitance (~5pf) and parasitic capacitance lowers this as frequency increases, but it usually still remains extremely high.