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Dfiference between demux and decoder

  1. Oct 29, 2005 #1
    could someone draw a clear distinction between these two for me? or are they basically the same?
    Decoder usually takes several inputs (2^n) and produces n outputs. Multiplexer is a switch but demultiplexer....if it's inverse of multiplexer than it has to have at least several inputs but the simplest mux has only 1 output, which means that if it is used as demux, it has only 1 input.
    Any clarification is greatly appreciated.
  2. jcsd
  3. Oct 29, 2005 #2
    I think a decoder takes n inputs and produces [tex]2^n[/tex] outputs. I know that it is possible to turn a decoder into a mux, not sure about a mux to decoder.
    Last edited: Oct 29, 2005
  4. Oct 30, 2005 #3
    Let's clarify:
    A decoder takes n inputs and produces 2^n outputs. An encoder takes 2^n inputs and produces n outputs.
    A multiplexer selects one line from many lines. The inverse of selection is distribution. A demux essentially transmits data from one line line to 2^n possible output lines. The output line is determined by n select lines. In short, a multiplexer selects an input line, a demultiplexer selects an output line.

    The differences between these two circuits is subtle, as far as I can tell. A demux simply selects an output line, nothing more. It's a glorified switch. A decoder takes n inputs, and uses those inputs to determine which of the 2^n output lines is high. This is the difference, I think. A decoder is designed to simply keep one line high. A demux is designed to set one output equal to the input (whether it be high, low, or a changing signal).

    I'm just learning this stuff myself, so if I made a mistake, please correct me.
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