I am designing a circuit and I am not sure which solution would be more preferred in the design. I'd like to justify why I'd use two 2:1 mux instead of a 4:1, but I don't seem to be able to. To be more specific, it looks like I'd have option 00 01 and 10 in the 4:1 mux. In the 2:1 muxes, ill have 0 and 1 and then the output will go to another mutex, also with option 0 and 1. Option 0 will be the output from the first mux and then if it is 1 I will have a different output.

Edit: People been asking for a diagram. PC is program counter.


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    \$\begingroup\$ These two see equivalent (if you connect (11 to C on the left one). I would go with the one requiring least components. So you will have to justify using two muxes instead of one to me as well :) \$\endgroup\$
    – Eugene Sh.
    Nov 21, 2019 at 16:01
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    \$\begingroup\$ What characteristics of the circuit matter to you? Speed? Number of components? Are you making this from transistors as VLSI logic, in an FPGA, or using off-the-shelf logic chips? \$\endgroup\$ Nov 21, 2019 at 16:47
  • \$\begingroup\$ It is like asking which phone should I buy Apple or Samsung ...Dude you have to say whats your preferences aka constraints ... \$\endgroup\$
    – Mitu Raj
    Nov 21, 2019 at 16:59

1 Answer 1


Functionally, the 4:1 mux could be seen as superior in that it allows you to later add a 4th input if you so desire; meanwhile, you can simply connect C to both the 3rd and 4th inputs as Eugene suggested to obtain a functionally identical circuit to a pair of 2:1s.

If the 2:1 muxes (muxs?) are individual ICs, then the 4:1 is also superior in terms of design simplicity; you only need to worry about powering one chip instead of two, and the layout is a simple 4-in, 1-out, rather than having to wire/route the output of the first 2:1 into the input of the second.

There could still be reasons why two 2:1s would be preferable to one 4:1, but I can't think of any off the top of my head other than if the cost were lower or another party had specifically requested 2:1s. If you want to use 2:1s out of personal preference, though, you can by all means - they'll do the job perfectly well.


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