MULTIPLEXER

A multiplexer is a combinational logic circuit. Multiplexer selects an input from a number of inputs and route it to a single output. Multiplexers usually have 4,8 and 16 inputs and a single output. A rotary switch is a classic example of mechanical multiplexing device. Here rotary switch has multiple contacts and a single rotor and thus can route any input to the output line. A 2 line to 1 line multiplexer require a control input, a NOT gate, two 2 input AND gates and an OR gate. A 4 line to 1 line multiplexer require two control inputs, two NOT gates, four 3 input AND gates and an OR gate. IC 74151 is a 8 line to 1 line multiplexer which has 8 input lines and 3 select inputs with a provision for a strobe (which is active low). IC 74150 is a 16 line to 1 line multiplexer which has 16 input lines and a single output. IC 74157 is a nibble multiplexer.