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Important Digital Logic and Design Short Questions

Chapter: 7
Question 1:
How does fan-out affect TTL and CMOS gates?
Answer: Fan-out is the maximum number of inputs that can be driven by a gate’s output. For TTL gates, high fan-out can decrease output voltage levels, while CMOS gates handle fan-out differently due to their high impedance.
Chapter: 7
Question 2:
What is the maximum fan-out of a TTL 7400 NAND gate?
Answer: The maximum fan-out of a TTL 7400 NAND gate is 10, meaning it can drive up to 10 similar gates.
Chapter: 7
Question 3:
What is the impact of loading on CMOS circuits?
Answer: Loading on CMOS circuits increases the input capacitance, which can reduce the maximum operating frequency.
Chapter: 8
Question 4:
What is the result of the Boolean operation A+BA + BA+B when A=1A = 1A=1 and B=0B = 0B=0?
Answer: The result is 111 because the OR operation yields 1 if any one of the inputs is 1.
Chapter: 8
Question 5:
How does the NOT gate affect a variable AAA?
Answer: The NOT gate inverts the value of AAA; if A=0A = 0A=0, then A‾=1\overline{A} = 1A=1 and vice versa.
Chapter: 8
Question 6:
What does the Boolean expression A.BA.BA.B represent in terms of logic gates?
Answer: The expression A.BA.BA.B represents an AND gate, where the output is 1 only if both AAA and BBB are 1.
Chapter: 8
Question 7:
State the Commutative Law for Boolean Addition.
Answer: The Commutative Law for Addition states that A+B=B+AA + B = B + AA+B=B+A, meaning the order of addition does not affect the result.
Chapter: 8
Question 8:
Explain the Associative Law for Boolean Multiplication with an example.
Answer: The Associative Law for Multiplication states that A.(B.C)=(A.B).CA.(B.C) = (A.B).CA.(B.C)=(A.B).C. For example, 1.(0.1)=(1.0).1=01.(0.1) = (1.0).1 = 01.(0.1)=(1.0).1=0, showing that the grouping of operations does not affect the result.
Chapter: 8
Question 9:
What is the Distributive Law in Boolean algebra?
Answer: The Distributive Law states A.(B+C)=A.B+A.CA.(B + C) = A.B + A.CA.(B+C)=A.B+A.C, which means multiplying a variable by a sum is the same as multiplying each term separately and then adding the results.
Chapter: 8
Question 10:
Simplify the Boolean expression A+A.BA + A.BA+A.B.
Answer: The expression simplifies to AAA, as A+A.B=A⋅(1+B)=A⋅1=AA + A.B = A \cdot (1 + B) = A \cdot 1 = AA+A.B=A⋅(1+B)=A⋅1=A according to Boolean rules.