# Digital Logic Assignment help plz

#### gonkar

Joined Oct 22, 2011
4
hi everybody,
the proff. assigned us this:
"Design a gate logic circuit to provide an output of 1 (true) when any two or more of the four inputs are 1"
plz help me approach this X)

#### hgmjr

Joined Jan 28, 2005
9,027
Sketch your attempt at a solution and then post it here.

hgmjr

#### joeyd999

Joined Jun 6, 2011
5,405
hi everybody,
the proff. assigned us this:
"Design a gate logic circuit to provide an output of 1 (true) when any two or more of the four inputs are 1"
plz help me approach this X)
Perhaps you should start with a truth table? From there a Karnough map should be elementary.

#### Georacer

Joined Nov 25, 2009
5,182
@gonkar

Shall we insist on you giving the truth table of your function? Do you know how to build it?

#### gonkar

Joined Oct 22, 2011
4
No u don't have to insist on me doing the truth table ^^
I'm working on that ... I'll post it when I'm done ... BRB ^___^

#### MrCarlos

Joined Jan 2, 2010
400
Hello gonkar

"Design a logic gate circuit to Provide an output of 1 (true) When two or more Any of the four inputs are 1"

This statement suggests several things:
1 - The circuit has 4 inputs.
2 - Two of them, either, if they are 1 the output should be 1.
3 - Naming the inputs as 1, 2, 3, 4, the possible combinations (any two) would
1 & 2, 1 & 3, 1 & 4.
2 & 3, 2 & 4.
3 & 4.
Right?

Because:
1, 2, 3, 4.------ Out
0, 0, 0, 0 -------- 0
0, 0, 0, 1 -------- 0
0, 0, 1, 0 -------- 0
0, 0, 1, 1 -------- 1 ----------( 3 & 4) Any Two.
0, 1, 0, 0 -------- 0
0, 1, 0, 1 -------- 1 ----------( 2 & 4) Any Two.
0, 1, 1, 0 -------- 1 ----------( 2 & 3) Any Two.
0, 1, 1, 1 -------- 1 ----------( 2 & 3) Or (2 & 4) or (3 & 4) Any Two Or More.
1, 0, 0, 0 -------- 0
1, 0, 0, 1 -------- 1 ----------( 1 & 4) Any Two.
1, 0, 1, 0 -------- 1 ----------( 1 & 3) Any Two.
1, 0, 1, 1 -------- 1 ----------( 1 & 3) Or (1 & 4) Or (3 & 4) Any Two Or More.
1, 1, 0, 0 -------- 1 ----------( 1 & 2) Any Two.
1, 1, 0, 1 -------- 1 ----------( 1 & 2) Or (1 & 4) Or (2 & 4) Any Two Or More.
1, 1, 1, 0 -------- 1 ----------( 1 & 2) Or (1 & 3) Or (2 & 3) Any Two Or More.
1, 1, 1, 1 -------- 1 ----------( 1 & 2) Or (1 & 3) Or (1 & 4) Or (2 & 3) Or (2 & 4) or (3 & 4) Any Two Or More.

So you need 6 2-input AND gates and an OR gate with 6 Inputs.

Greetings

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