As the title says I have problem with understanding how to make the truth table for demultiplexer and how to make a Boolean expression from it. The thing that bothers me is how to make a truth table with more than one outputs. I search through google and I've found this answer

However I can't understand it, and I have no idea what to do. Any help is appreciated.

I got it, in case anybody came here with search engine, read the comments, and don't Or(+) the outputs.

  • 1
    \$\begingroup\$ Make a separate truth table for each output. As the set of input patterns is the same for each table, you can then combine all your tables into one, with the same inputs, and a separate column for each output. \$\endgroup\$
    – user16324
    Sep 6, 2015 at 20:14
  • \$\begingroup\$ And how can I draw the Boolean expression them. I mean in one case a will be = to 1, in the other b will be = to 1, is another both of them will be 1? And then I have to proceed like turning truth table with one input into Boolean expression? \$\endgroup\$ Sep 6, 2015 at 20:21
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    \$\begingroup\$ You will need a Boolean equation for each output based upon the inputs. \$\endgroup\$ Sep 6, 2015 at 20:30
  • \$\begingroup\$ And then I have just to Or(+) them? \$\endgroup\$ Sep 6, 2015 at 20:33
  • \$\begingroup\$ Depends. Do you or your outputs in the final circuit? \$\endgroup\$ Sep 6, 2015 at 20:46

1 Answer 1


Following is the truth table for a sixteen-to-one demultiplexer.

A0 through A3 are the output address select inputs, and are used to steer the digital input signal on E1 bar to the output corresponding to the port pointed to by the address select inputs, as long as E2 bar is low.

If you need to construct the Boolean equation for each state, then all you have to do is to collect the terms required to make that state unique and relate them properly.

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