logic circuit

logic circuit electric circuit whose output depends upon the input in a way that can be expressed as a function in symbolic logic ; it has one or more binary inputs (capable of assuming either of two states, e.g., "on" or "off" ) and a single binary output. Logic circuits that perform particular functions are called gates. Basic logic circuits include the AND gate, the OR gate, and the NOT gate, which perform the logical functions AND, OR, and NOT. Logic circuits can be built from any binary electric or electronic devices, including switches , relays , electron tubes , solid-state diodes , and transistors ; the choice depends upon the application and design requirements. Modern technology has produced integrated logic circuits, modules that perform complex logical functions. A major use of logic circuits is in electronic digital computers. Fluid logic circuits have been developed whose function depends on the flow of a liquid or gas rather than on an electric current.

logic circuit An electric circuit concerned with logic systems. The term logic device is often used synonymously. A logic circuit is required to produce specified binary outputs as a result of specified binary inputs. This may be accomplished by using logic gates, producing what is called hardware circuitry. Alternatively the inputs may be associated with the address lines of a ROM and the outputs with the data lines of a ROM; this is called firmware circuitry.

Hardware circuitry constructed from integrated-circuit packages on circuit boards requires two types of wiring. The first type carries the logic information between gates. The second type provides the power for the individual chips. The process of locating the power paths so that they do not interfere with the logic paths is called power routing.

Logic circuitry may be mathematically analyzed using Boolean (or switching) algebra. In this representation the binary 1 is associated with the identity element and the logic 0 is associated with the null element, i.e. zero.

See also combinational circuit, sequential circuit, digital logic, multivalued logic.