# Need help making a logic circuit

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ok so im in this intro computer science class and we just started doing circuits and I seem to be stumped on this problem. I bet a lot of people here could do this problem while they are asleep so...... anyone wanna help me out  .

(problem is the attacked image)

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peeps...it would seem to me that A...and B...both go to an andgate with the control signal being the second leg on each. They resove to an orgate that becomes the output.

Looks good from here...

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I don't think that works because if i set the control signal to 1 (so the output should be the same as A) and i set the A input to 0 and the B input to 1, the output is a 1 when it should be 0 because A is 0.

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the problem doesn't indicate that A..or ..B ..ever change.....I read it as ..A>..being a voltage level..perhaps....and B..something like gnd.

It only indicates that the control signal changes...

and the orgate may need a state indicator on the B line to make it pass...

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Yea, im not really sure, but I tested ur idea and i think i figured it out.

Put A into and AND gate and B into and XOR gate and the control signal into both of those, and then the outputs of those two into an OR gate and it works out i believe.

Thanks for the help Aggr3

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ok nevermind it doesn't work...... i hate computer science

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you can thank me later

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its a sloppy drawing...the last logic object before out is the OR rage....

........sorry for a bad drawing lol

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i corrected my sloppy drawing lol

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i dont know if you know this much....but what you are actually designing is a simple multiplexer....

a multiplexer (mux) is simply a switch that passes either of its inputs through as the output

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oh...and i just re-read the question.....

just switch A and B - since my design will give you A if control is 0, not if its 1 (as the question asked)

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i dunno if im reading the question wrong or if im making some stupid mistake, but to me it appears that your logic circuit doesn't work. If you set A = 0 and B = 1 and the controller = 1; then the output is 1, even though it should be 0.

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refer to my post ^^^^^^ ... just switch A and B

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refer to my post ^^^^^^ ... just switch A and B

yea i tried that and the result is still the same.

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im drawing up a new one....give me a sec...i thought ud see an answer up untill now...its right there

here you go

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wow, i feel like an idiot i was saying that 0 + 1 in an AND gate came out to 1............

Disturbed ty for bearing with my ignorance and helping me out  .

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no problemo

what are you using for simulation ? logicworks ?

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what are you using for simulation ? logicworks ?

No, I was just running through it with a piece of paper / pen. This is pretty much my first computer science class ever so I'm a newbie. I might have to look into that logicworks though .

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