Majority function question

Discussion in 'Homework Help' started by jegues, Sep 25, 2010.

  1. jegues

    Thread Starter Well-Known Member

    Sep 13, 2010
    Problem Statement:
    A four-variable logic function that is equal to 1 if any three or all four of its variables are equal to 1 is called a ​
    majority function. Design a minimum-cost SOP circuit that implements the majority function.

    The function I got is as follows,

    x_{1}x_{2} + x_{3}x_{4}

    They list the answer as something with more gates but I can't see how this one doesn't work just fine.

    Are they wrong, or am I just crazy?​

  2. Ghar

    Active Member

    Mar 8, 2010
    Create a truth table for the problem statement and you'll find your function doesn't satisfy it.

    For example, your function outputs a 1 if x1 and x2 are 1.
    That isn't a majority since only 2 of the 4 inputs are 1.
    Similarly this happens when x3 and x4 are 1.