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. The number of states in a 3-bit Johnson (twisted ring) counter is:

    Answer: 6

    A Johnson counter with n flip-flops has 2n states, so 3 flip-flops yield 6 valid states.

  2. In two's complement representation, what is −5 in 4 bits?

    Answer: 1011

    +5 is 0101; inverting gives 1010, adding 1 gives 1011, which is −5 in two's complement.

  3. A half-adder can be implemented using which pair of gates?

    Answer: XOR and AND

    A half-adder uses an XOR gate for the sum and an AND gate for the carry output.

  4. Which of the following expressions is in its minimal Sum of Products (SOP) form for F(A,B,C)=Σm(1,3,5,7)?

    Answer: C

    All minterms have C=1 regardless of A and B, so the minimal SOP is simply C.

  5. What is the primary advantage of a Look-Ahead Carry Adder over a Ripple Carry Adder?

    Answer: Faster carry computation

    Look-ahead carry adders compute carry signals in parallel, greatly reducing propagation delay.

  6. An SR latch enters a forbidden (invalid) state when:

    Answer: S=1, R=1

    When both S=1 and R=1, both outputs are forced to 0, creating an undefined/invalid state.

  7. How many minterms does the Boolean function of 3 variables have?

    Answer: 8

    A function of n variables has 2^n minterms; for n=3, that is 2^3 = 8.