Combinational Circuits
A combinational circuit consists of logic gates where the outputs at any given moment are determined solely by the current combination of inputs, with no dependence on prior inputs.
A combinational circuit carries out a specific information-processing task, completely defined by a set of Boolean functions.
The fundamental components of a combinational circuit include input variables, logic gates, and output variables.
The 'n' input variables are supplied by an external source, while the 'm' output variables are sent to an external destination. In many cases, the source or destination consists of storage registers.
Design procedure of a Combinational Circuit
The process of designing a combinational circuit includes the following steps:
- The problem is stated.
- The total number of available input variables and required output variables is determined.
- The input and output variables are allocated with letter symbols.
- The exact truth table that defines the required relationships between inputs and outputs is derived.
- The simplified Boolean function is obtained from each output.
- The logic diagram is drawn.
A combinational circuit that adds two bits is known as a half adder, while a circuit that adds three bits (two significant bits and a carry from a previous operation) is called a full adder.
