Both multiplexers and decoders play significant roles in the transfer of signals in many communication systems. Although they perform similar functions, there are notable differences between them.
What is a Multiplexer?
A multiplexer, also known as a MUX, is a combinational digital circuit that actively selects one input signal out of several options and transmits the chosen signal to a single output line. It functions as a data selector by picking a specific input from multiple inputs and delivering it to a designated output line. The operational principle of a multiplexer is based on the concept of merging multiple inputs into one output, following a many-to-one approach.
What is Decoder?
On the other hand, a decoder is another type of combinational logic circuit that consists of multiple input and output lines. A decoder typically has “n” input lines and a maximum of “m” output lines, where the value of “m” equals 2 to the power of “n” (m = 2^n). When the decoder circuit is enabled, it examines the combination of inputs present and activates one of the 2^n output lines accordingly. This means that only one specific output line will be active high based on the input combination. The block diagram of a decoder is illustrated in Figure 2.
Difference between Multiplexer and Decoder
Here is a simplified table highlighting the differences between a multiplexer and a decoder:
| Basis of Difference | Multiplexer | Decoder |
|---|---|---|
| Definition | A circuit with 2n inputs and 1 output. | A circuit with n inputs and a maximum of 2n outputs. |
| Operation | Selects one input and transmits it to the output. | Converts input codes into corresponding output signals. |
| Primary function | Transmits data and signals. | Interprets coded data. |
| Controlling of operation | Select lines control the operation, determining which input passes to the output. | Enable input controls the operation. |
| Input lines | Has 2n input lines. | Has n input lines. |
| Output lines | Has 1 output line. | Has 2n output lines. |
| Types | Common types include 8:1, 16:1, and 32:1 multiplexers. | Common types include 2:4, 3:8, and 4:16 decoders. |
| Applications | Used in communication systems, data routing, waveform generation, computer memories, etc. | Used in seven-segment displays, memory address decoding, control units, networking, telecommunication systems, etc. |