Illustrate functional diagram of digital multiplexer. Write the scheme of a 4- input multiplexer using basic gates (AND/OR/NOT) and explain its operation.

Ans:

Multiplexer: Data selector or MUX is a logic circuit selects binary information from one of several input and directs this to a single output line. Selection of the individual input line is controlled through a set of selection lines. Generally there are 2n input lines and respectively n selection lines.

Here 4 inputs that are I₁ I₀ I₂ I₃ and two selection line as S₀ and S₁. Depending on the bit combination of S₀ and S₁ one of the inputs is moved to the output. Fundamentally there is a decoder circuit along with one input for each bit of information and one OR gate linked to the output. If S_o, S_i = 00, then first AND gate will contain the two inputs as one output will depend upon I₀. At similar time outputs of all other AND gates are Zero.

The multiplexer is a combinational circuit that is individual most broadly utilized standard circuit in digital design. This has N select lines 2^N inputs and a particular output.

Multiplexer:-

Y = S‾₁S‾₀ I₀ + S‾₁S₀ I₁ + S₁S‾₀I₂  + S₁S₀ I₃

Truth table of 4x1 Mux

Circuit Diagram of 4 X 1 MUX using basic gate