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GATE 2018 EE – Question 46

Analog and Digital Electronics · VCOs and timers, combinatorial and sequential logic circuits, multiplexers, demultiplexers · 2 marks · Multiple choice

Which one of the following statements is true about the digital circuit shown in the figure?

Diagram for GATE 2018 EE question 46
  1. It can be used for dividing the input frequency by 3.
  2. It can be used for dividing the input frequency by 5.
  3. It can be used for dividing the input frequency by 7.
  4. It cannot be reliably used as a frequency divider due to disjoint internal cycles.

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Show answer and explanation

Correct answer: (B) It can be used for dividing the input frequency by 5.

Explanation

The three D flip-flops form a shift register whose serial input is taken from the NAND of two of the outputs. Following the state sequence from the initial state around the feedback loop gives a cycle of length 5, so the output frequency is the input frequency divided by 5 (the official key).