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Questions and Answers
Which of the following basic logic functions are represented by symbols?
Which of the following basic logic functions are represented by symbols?
- AND
- OR
- NOT
- All of the above (correct)
A truth table completely specifies the outputs of a logic function for all possible input combinations.
A truth table completely specifies the outputs of a logic function for all possible input combinations.
True (A)
What is the output of an inverter when the input is 0?
What is the output of an inverter when the input is 0?
- 1 (correct)
- 0
What is the name of the logic gate represented by the symbol '•'?
What is the name of the logic gate represented by the symbol '•'?
Which of the following statements describes the behavior of an AND gate? (Select all that apply)
Which of the following statements describes the behavior of an AND gate? (Select all that apply)
What is the output of an OR gate if one input is high and the other is low?
What is the output of an OR gate if one input is high and the other is low?
What is the output of a NAND gate when both inputs are high?
What is the output of a NAND gate when both inputs are high?
The NAND gate is considered a 'logically complete set' because it can be used to implement any other logic gates.
The NAND gate is considered a 'logically complete set' because it can be used to implement any other logic gates.
Which of the following logic gates is NOT considered a 'logically complete set'?
Which of the following logic gates is NOT considered a 'logically complete set'?
A NOR gate is a combination of an OR gate followed by an inverter.
A NOR gate is a combination of an OR gate followed by an inverter.
What is the output of a NOR gate when both inputs are low?
What is the output of a NOR gate when both inputs are low?
The NOR gate, like the NAND gate, is a 'logically complete set' and can be used to implement all other logic gates.
The NOR gate, like the NAND gate, is a 'logically complete set' and can be used to implement all other logic gates.
What is the output of an XOR gate when the two inputs are at opposite levels?
What is the output of an XOR gate when the two inputs are at opposite levels?
What is the output of an XNOR gate when the two inputs are at the same level?
What is the output of an XNOR gate when the two inputs are at the same level?
Which of the following methods can be used to represent the functionality of digital logic circuits?
Which of the following methods can be used to represent the functionality of digital logic circuits?
Waveforms are a visual representation of signal behavior over time, with high levels typically representing logic 1 and low levels representing logic 0.
Waveforms are a visual representation of signal behavior over time, with high levels typically representing logic 1 and low levels representing logic 0.
What is the primary purpose of Boolean algebra in digital logic design?
What is the primary purpose of Boolean algebra in digital logic design?
Which of the following is NOT a Boolean algebraic rule?
Which of the following is NOT a Boolean algebraic rule?
The 'complement' of a variable (a) in Boolean algebra is denoted as 'a' or 'ā' and represents the inverse of that variable's logic level.
The 'complement' of a variable (a) in Boolean algebra is denoted as 'a' or 'ā' and represents the inverse of that variable's logic level.
Who is credited with developing the foundational concept of Boolean algebra?
Who is credited with developing the foundational concept of Boolean algebra?
What is the Commutative Law of ORing in Boolean algebra?
What is the Commutative Law of ORing in Boolean algebra?
The Associative Law of ANDing in Boolean algebra states that the order of grouping variables in an AND operation does not affect the result.
The Associative Law of ANDing in Boolean algebra states that the order of grouping variables in an AND operation does not affect the result.
What Boolean algebraic law describes the following equality: A(B + C) = AB + AC?
What Boolean algebraic law describes the following equality: A(B + C) = AB + AC?
De Morgan's Theorems provide a way to:
De Morgan's Theorems provide a way to:
One of De Morgan's Theorems states that the complement of a product is equal to the sum of the complements of its individual variables.
One of De Morgan's Theorems states that the complement of a product is equal to the sum of the complements of its individual variables.
In Boolean algebra, what is a 'literal'?
In Boolean algebra, what is a 'literal'?
What is a 'product term' in Boolean algebra?
What is a 'product term' in Boolean algebra?
A 'sum-of-products' (SOP) expression in Boolean algebra consists of a sum (OR) of multiple product terms.
A 'sum-of-products' (SOP) expression in Boolean algebra consists of a sum (OR) of multiple product terms.
Which of the following Boolean expressions is in the 'sum-of-products' (SOP) form?
Which of the following Boolean expressions is in the 'sum-of-products' (SOP) form?
A 'product of sums' (POS) expression consists of a product (AND) of multiple sum terms.
A 'product of sums' (POS) expression consists of a product (AND) of multiple sum terms.
What is the Boolean expression for a majority detector that outputs a logic 1 when at least two out of three inputs (A, B, C) are high?
What is the Boolean expression for a majority detector that outputs a logic 1 when at least two out of three inputs (A, B, C) are high?
What is a 'minterm' in Boolean algebra?
What is a 'minterm' in Boolean algebra?
Every logic function can be expressed algebraically by combining all the minterms corresponding to the rows where the function outputs a 1, using the OR operation.
Every logic function can be expressed algebraically by combining all the minterms corresponding to the rows where the function outputs a 1, using the OR operation.
If a truth table has 4 input variables, how many rows will it have?
If a truth table has 4 input variables, how many rows will it have?
What is the relationship between the number of 1's in the truth table output column and the number of AND terms needed for a Sum-of-Products (SOP) expression?
What is the relationship between the number of 1's in the truth table output column and the number of AND terms needed for a Sum-of-Products (SOP) expression?
To convert a Boolean expression to a logic circuit, you would typically use AND gates for the product terms and an OR gate for the sum operation.
To convert a Boolean expression to a logic circuit, you would typically use AND gates for the product terms and an OR gate for the sum operation.
Flashcards
Inverter Truth Table
Inverter Truth Table
A table showing the output for all possible input combinations of an inverter.
AND Gate Truth Table
AND Gate Truth Table
A table that shows the output of an AND gate for all possible combinations of input values.
OR Gate Truth Table
OR Gate Truth Table
A table specifying the output for all possible input combinations of an OR gate.
NAND Gate
NAND Gate
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NAND Universal Property
NAND Universal Property
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NOR Gate
NOR Gate
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Study Notes
Digital Logic Design
- Course: NET 104
- Lecture: 2+3
- Date: 10/19/2024
Describing Circuit Functionality: Inverter
- Basic logic functions have symbols
- Functionality is represented by truth tables
- Truth tables specify output for all input combinations
- Inverter inverts input 0 to 1 and input 1 to 0
The AND Gate
- AND gate has two input signals
- If both inputs are asserted (high), the output is also asserted (high)
- Otherwise, the output is deasserted (low)
- Y = A.B
The OR Gate
- OR gate has two input signals
- If either or both inputs are asserted (high), the output is also asserted (high)
- Otherwise, the output is deasserted (low)
- Y = A + B
The NAND Gate
- NAND gate is a combination of AND gate followed by an inverter
- NAND(A, B) = (A AND B)'
- Output is 1 if at least one input is zero
The Universal Property of NAND
- NAND gates can implement NOT, AND, and OR gates
- Therefore, NAND alone is a logically complete set
The NOR Gate
- NOR gate is a combination of an OR gate followed by an inverter
- NOR(A, B) = (A + B)'
- Output is 0 if at least one input is one
The Universal Property of NOR
- NOR gates can implement NOT, AND, and OR gates
- Therefore, NOR alone is a logically complete set
Exclusive-OR Circuits
- Exclusive-OR (XOR) produces a HIGH output when the two inputs are at opposite levels
- X = AB + AB
Exclusive-NOR Circuits
- Exclusive-NOR (XNOR) produces a HIGH output when the two inputs are at the same level
- X = AB + AB
XOR Function
- XOR function can be implemented using AND/OR gates (and also NANDs)
Describing Circuit Functionality: Waveforms
- Waveforms represent functionality by high (logic 1) and low (logic 0) values
- Truth tables can be created from waveforms
Consider Three-input Gates
- Three-input OR gate: X = A + B + C
Boolean Algebra
- Useful for identifying and minimizing circuit functionality.
- Identity elements: a + 0 = a, a • 1 = a
- 0 is the identity element for the + operation; 1 for the • operation
- Complements: For every element a, there exists a unique element a' (or ā) such that a + a' = 1 and a • a' = 0
George Boole (1815 - 1864)
- Father of Boolean algebra
- Developed a system based on a binary approach: yes-no, true-false, on-off, or zero-one.
- His ideas weren't widely accepted until Claude Shannon adopted and developed them later.
Laws of Boolean Algebra
- Commutative Law of ORing: A + B = B + A
- Commutative Law of ANDing: A • B = B • A
- Associative Law of ORing: A + (B + C) = (A + B) + C
- Associative Law of ANDing: A • (B • C) = (A • B) • C
- Distributive Law: A • (B + C) = AB + AC
Rules of Boolean Algebra
- Various rules for simplification and manipulation of Boolean expressions.
De Morgan's Theorems
- Rules for converting between AND and OR operations
- A • B = A + B
- A + B = A • B
- Generalizations apply to multiple variables
De Morgan's Theorems Example
- Examples showing applications of De Morgan's theorems in Boolean algebra.
Converting AND to OR
- Using De Morgan's Theorems, AND gates can be converted to OR gates (and vice versa). Invert the inputs and output.
Standard Forms of Boolean Expressions
- Sum-of-products (SOP) form: Example: X = AB + CD + EF
- Product-of-sums (POS) form: Example: X = (A + B)(C + D)(E + F)
Sum-of-Products Expression
- A literal is a variable in its complemented or uncomplemented form.
- Defines the product term in algebraic form.
From Truth Table to Boolean Expression
- Any logic function in a truth table can be expressed algebraically using sums of minterms.
Converting to a Circuit
- Converting a Boolean expression to a circuit using AND and OR gates.
Thank You
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