logicgate

A logic gate is a basic building block of digital circuits that performs a Boolean operation on one or more binary inputs to produce a binary output. Each gate implements a specific logic function, typically summarized by a truth table. The most common gates are AND, OR, and NOT, but any of the basic operations can be combined to form NAND, NOR, XOR, and XNOR gates.

Logic gates are realized physically in integrated circuits using transistor technologies such as TTL (transistor-transistor logic) and CMOS (complementary metal-oxide-semiconductor). Gates have characteristics including propagation delay and fan-in (the number of inputs) and fan-out (the number of inputs they can drive). Some gates are universal, notably NAND and NOR, meaning any Boolean function can be constructed using only that gate type.

In digital design, gates are used to build combinational circuits in which outputs depend only on current inputs, as well as sequential circuits that rely on feedback and memory elements like flip-flops and latches. Boolean algebra, truth tables, and graphical tools such as Karnaugh maps are used to analyze and minimize circuits to reduce gate count and delay.

History: The concept derives from Boolean algebra, established by George Boole in the 19th century, and was applied to electrical circuits in the mid-20th century, notably by Claude Shannon. Since then logic gates have been realized in numerous families and remain essential to computing, digital control, and information processing.