Practice Test Geeks(GATE) Graduate Aptitude Test in Engineering Practice Test
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Digital Logic Flashcards

7 cards from real GATE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Digital Logic flashcards as text

  1. Which Boolean expression represents the output of an XNOR gate with inputs A and B?

    Answer: A·B + A'·B'

    XNOR outputs 1 when both inputs are equal, expressed as A·B + A'·B'.

  2. A 4-bit ripple carry adder adds two 4-bit numbers. What is the maximum number of gate delays for carry propagation?

    Answer: 8

    Each full adder introduces 2 gate delays for carry, so 4 stages yield 8 gate delays total.

  3. The minimum number of NAND gates required to implement the function F = A·B + C is:

    Answer: 3

    F = A·B + C can be realized with 3 NAND gates: NAND(A,B), NAND(C,C), and NAND of their outputs.

  4. In a JK flip-flop, what is the output when J=1, K=1 and a clock pulse is applied?

    Answer: Q toggles to complement

    When J=K=1, the JK flip-flop toggles its output on each clock pulse.

  5. Which of the following is a universal gate?

    Answer: NAND

    NAND (and NOR) are universal gates because any Boolean function can be implemented using only NAND gates.

  6. The decimal number 45 in BCD (Binary Coded Decimal) is represented as:

    Answer: 0100 0101

    BCD encodes each decimal digit separately: 4 = 0100, 5 = 0101, giving 0100 0101.

  7. A multiplexer with n select lines can have at most how many input lines?

    Answer: 2^n

    An n-select-line multiplexer can select among 2^n inputs, one per select combination.