When used with an IC, what does the term "QUAD" indicate?
Answer: B
Correct answer: 4 circuits
The prefixes count the independent gates in the package: dual two, triple three, quad four, hex six. A quad two-input NAND, the 7400, holds four separate gates.
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How many pins does the 4049 IC have?
Answer: B
Correct answer: 16
The 4049 is a hex inverting buffer, and its package has 16 pins - six inverters using twelve pins, plus supply and ground, with two pins unused.
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If a logic gates has four inputs, then total number of possible input combinations is
Answer: C
Correct answer: 16
Each input can be 0 or 1 independently, so n inputs give \( 2^n \) combinations, and \( 2^4 = 16 \).
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The number of input combinations for a 4-input gate is ________.
Answer: D
Correct answer: 16
Each input takes two values independently, so four inputs give \( 2^4 = 16 \) combinations.
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The dual ofthe switching function x + yz is:
Answer: C
Correct answer: x(y+z)
The dual of an expression is formed by exchanging AND with OR and 0 with 1, leaving the variables uncomplemented. Applying that to \( x + yz \) turns the outer OR into AND and the inner AND into OR, giving \( x(y+z) \). Complementing the variables would give the complement, not the dual.
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The output of an exclusive-NOR gate is HIGH if ________.
Answer: A
Correct answer: the inputs are equal
XNOR is the complement of XOR, so where XOR detects difference, XNOR detects agreement. It is HIGH when both inputs are 0 and when both are 1.
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How many lines the truth table for a four-input NOR gate would contain to cover all possible input combinations ?
Answer: D
Correct answer: 16
A truth table has one row for each combination of input values, and n inputs give \( 2^n \) combinations. With four inputs that is \( 2^4 = 16 \).
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The output of a NOR gate is HIGH if ________.
Answer: D
Correct answer: all inputs are LOW
NOR is the complement of OR, and OR is 0 only when every input is 0, so NOR is 1 in exactly that case.
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Which of the following statements is wrong ?
Answer: C
Correct answer: Fan-in of a gate is always equal to fan-out of the same gate
Fan-in is the number of inputs a gate has and fan-out the number of gate inputs its output can drive; the two are independent properties and there is no reason for them to be equal. The other three statements are the standard definitions of propagation delay, noise immunity and operating speed.
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What is the Boolean expression for a three-input AND gate?
Answer: B
Correct answer: X = A · B · C
AND is a product, written with dots or by juxtaposition. The plus sign denotes OR, and the other two symbols have no meaning in Boolean algebra.
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