Digital Logic · Unit 2
Boolean Algebra and Logic Gates
Exam-focused notes for Boolean Algebra and Logic Gates (Digital Logic, BIT103): what the TU syllabus asks and how it has actually been tested, with 5 solved past questions from this unit.
What this unit covers
- Boolean theorems and De Morgan's laws
- Logic gates and universal gates
- NAND and NOR gate realization
- Exclusive-OR and exclusive-NOR gates
- Boolean function simplification
NAND and NOR gate realization
Why NAND and NOR gates are called Universal logic gates? Realize NOR as Universal logic gates. [5]
NAND and NOR gates are called universal logic gates because any Boolean function or logic circuit can be implemented using only NAND gates or only NOR gates, without needing any other type of gate (AND, OR, NOT). In other words, the three basic gates (NOT, ...
Full solved answer →Boolean theorems and De Morgan's laws
State and prove De-Morgan's Theorems. [5]
De-Morgan's Theorems are two fundamental theorems in Boolean algebra: Theorem 1: $$\overline{A + B} = \overline{A} \cdot \overline{B}$$ "The complement of a sum equals the product of the complements." Theorem 2: $$\overline{A \cdot B} = \overline{A} + \over...
Full solved answer →Exclusive-OR and exclusive-NOR gates
Show that the dual of the exclusive-OR is equal to its complement. [5]
- Function: Exclusive-OR, $F = A \oplus B = A\bar{B} + \bar{A}B$ - To prove: $F^D = \bar{F}$ (dual equals complement) --- Dual of a Boolean expression: Interchange AND (·) with OR (+), and interchange 0 with 1. Variables (and their complements) remain uncha...
Full solved answer →Show that the dual of the exclusive-OR is equal to its complement. [5]
Exclusive-OR (XOR): $$A \oplus B = A'B + AB'$$ Dual of a Boolean function: Replace every AND (·) with OR (+), every OR (+) with AND (·), every 1 with 0, and every 0 with 1. (Variables and their complements are left unchanged.) Complement of a function: Appl...
Full solved answer →Logic gates and universal gates
Write short notes on (a) Universal gate. (b) Status register. [2.5+2.5]
--- A universal gate is a logic gate that can be used to implement any Boolean function or any other logic gate (AND, OR, NOT, etc.) without needing any other type of gate. The two universal gates are: - NAND Gate - NOR Gate Because all basic gates can be r...
Full solved answer →Make Unit 2 stick
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