4 x 1 mux using logic gates

I need to build a 4 x 1 mux using only logic gates. Can someone help me, I don't even know where to start?

by jkary
November 15, 2016

2 Answers

Answer by agiustino45

Yes, thats totally possible. The first thing to do is to get a 2 x 1 mux working. In this design I use AND, a NOT gate, and an OR gate. Its not super easy to see how this works by just staring at it, but I suggest you play with the inputs and see the results at each stage of the circuit to get a handle of how it works.

Once we have a two input mux working you need to chain them together to make your 4 input mux.

Notice how you can use one selection input to mux between the "top" or "bottom" input of each of your 2 input muxes, and then use another to select between the outputs of your first stage. I hope that makes sense!

+2 votes
by agiustino45
November 16, 2016

Answer by dnadya

Isnt a mux a logic gate already? Do you mean how do you make a 4x1 mux out of 2x1 muxes? That's pretty easy.

Click and run - it simulates! I made it be an XOR but you can change the "0" and "1" bits on the data inputs (in00, in01, in10, in11) and make it do whatever.

That's a way to do it with three 2x1 muxes. Two stages, one for each bit of the selector.

+1 vote
by dnadya
November 16, 2016

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