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Question

Consider the following 4-variable Boolean function

$F(A, B, C, D) = \Sigma m(0, 1, 2, 3, 8, 9, 10, 11)$

Consider $A$ as MSB, $D$ as LSB. Which one of the following options represents the minimal sum of products form for the above function?
Note: $+$ is OR operation, $.$ is AND operation, $'$ is NOT operation

The correct answer is
$B'$

Understanding the Boolean Function and Minterms

The given Boolean function is defined by its minterms: $F(A, B, C, D) = \Sigma m(0, 1, 2, 3, 8, 9, 10, 11)$. This signifies that the function output is 1 for these specific input combinations. Variable $A$ is the MSB and $D$ is the LSB.

Constructing the Karnaugh Map (K-map)

A 4-variable Karnaugh map (K-map) is constructed to simplify the function. The map uses AB for rows and CD for columns. Cells corresponding to the given minterms are marked with '1'.

4-Variable K-Map
CD ↓ &brbar AB → 00 01 11 10
($A'B'$) ($A'B$) ($AB$) ($AB'$)
00 ($C'D'$) 1 0 0 1
01 ($C'D$) 1 0 0 1
11 ($CD$) 1 0 0 1
10 ($CD'$) 1 0 0 1

Grouping '1's for Minimal SOP

To achieve the minimal Sum of Products (SOP) form, adjacent '1's in the K-map are grouped into the largest possible blocks (powers of 2).

  • Group 1: The first column (cells corresponding to $A'B'$) contains four '1's (minterms 0, 1, 2, 3). This yields the term $A'B'$.
  • Group 2: The last column (cells corresponding to $AB'$) contains four '1's (minterms 8, 9, 10, 11). This yields the term $AB'$.

These two groups are essential and collectively cover all '1's.

Deriving the Minimal Sum of Products (SOP)

The minimal SOP is the OR combination of the terms derived from the groups.

Function $F = A'B' + AB'$

Simplifying the Expression

Boolean algebra rules are applied for simplification.

Factor out the common term $B'$:

$F = B'(A' + A)$

Using the identity $X + X' = 1$, we get $A' + A = 1$.

$F = B'(1)$

Using the identity $X \cdot 1 = X$, the simplified expression is:

$F = B'$

This minimal SOP form matches Option B.

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Important Questions from Minimization of Boolean Expression

  1. Consider the following four variable Boolean function in sum-of-product form

    $F(b_3, b_2, b_1, b_0) = \sum(0, 2, 4, 8, 10, 11, 12)$.

    where the value of the function is computed by considering $b_3b_2b_1b_0$ as a 4-bit binary number, where $b_3$ denotes the most significant bit and $b_0$ denotes the least significant bit. Note that there are no don't care terms. Which ONE of the following options is the CORRECT minimized Boolean expression for F?

  2. Simplified Boolean equation for the following truth table is :
    xyzF
    0000
    0011
    0100
    0111
    1001
    1010
    1101
    1110
  3. The simplified form of a Boolean equation $(A\overline{B} + A\overline{B}C + AC)(\overline{A}\overline{C} + \overline{B})$ is :

  4. Simplify the following Boolean expression.

    E(E + F) + DE + D(E + F)

  5. What is the value of \( \bar{F}\)?

    \(F = AB + \bar{C}\bar{D} + \bar{B}D\)

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