Understand Multiplexers

Do you know the multiplexer? Commonly known as a MUX, it is quite a fundamental logic circuit in electronic circuits. Its function is to "synthesize signals" or "select what you want from the signals" and output it. Although its function is simple in itself, due to its high versatility, it has been used in various applications such as electronic circuits and communication businesses like fiber optics and telephone lines.

What is a multiplexer?

First of all, "multiplexing" refers to transmitting data by synthesizing multiple data using only one transmission line. Whether it is an analog circuit or a digital circuit, a device will input many signals. However, only one line can be used normally. If we set up a line for each signal, the device will be very complex and very large. Therefore, by installing a multiplexer, while sharing the transmission line, you can arbitrarily combine the input signals or select any signal from the input signals to determine the output signal. Due to these characteristics, multiplexers are installed at the transmitting end of the signal. Conversely, a device that converts one signal into multiple signals is called a demultiplexer.

Multiplexer Configuration

Logical circuits with characteristics similar to multiplexers are classified as"combinational circuits." A combinational circuit is a logic circuit whose output signal is determined solely by "what input is made." The opposite is sequential circuits, where the output signal is determined not only by "input" but also by "how it was output previously." Since sequential circuits have triggers, they have the function of holding data.

Multiplexers are combinational circuits, composed of multiple AND circuits, OR circuits, and NOT circuits. It usually has n control inputs, 2 to the nth power inputs, and one data output. When the program controls these logic gates, it operates by transmitting and controlling multiple input signals to the output. As mentioned above, everything depends solely on the input signal, so when the input signal switches, the output signal changes immediately. In addition, multiple multiplexers themselves can be connected together to form a larger multiplexer. There are several of these multiplexers in a computer, playing more complex switching and filtering roles.

Multiplexers Used with Demultiplexers

In most cases, it is used with a demultiplexer. By connecting the output signal selected by the multiplexer to the input side of the demultiplexer, the transmission line can be shared complementarily, thereby saving space.

In communications and the like, signals go back and forth between sending and receiving, so a basic circuit is needed to determine both parties' input/output signals. Even if this multiplexeris combined with a demultiplexer, it is still called a"multiplexer." By using both a multiplexer and a demultiplexer, serial transmission and parallel transmission can be performed, and digital control can be applied to analog circuits. The multiplexer in communication is installed at the "transmission" end of the communication. With a multiplexer, multiple transmitted data streams can be combined (multiplexed) to form a single stream. It does not need a transmission line for each data stream, and it can be transmitted on a single link (and received by installing a demultiplexer together). In the demultiplexer, the combined stream is reversed into the original multiple streams, so it is installed at the receiving end.