1. What is DeMorgan's theorem?

Answer

For N variables, DeMorgan’s theorems are expressed in the following formulas:

(ABC..N)' = A' + B' + C' + ... + N' -- The complement of the product is equivalent to the sum of the complements.

(A + B + C + ... + N)' = A'B'C'...N' -- The complement of the sum is equivalent to the product of the complements.

This relationship so induced is called DeMorgan's duality.

2. F'(A, B, C, D) = C'D + ABC' + ABCD + D. Express F in Product of Sum form.

Answer

Complementing both sides and applying DeMorgan's Theorem:

F(A, B, C, D) = (C + D')(A' + B' + C)(A' + B' + C' + D')(D')

3. How many squares/cells will be present in the k-map of F(A, B, C)?

Answer

F(A, B, C) has three variables/inputs.

Therefore, number of squares/cells in k-map of F = 2^{(Number of variables)} = 2^{3} = 8.

4. Simplify F(A, B, C, D) = Σ ( 0, 1, 4, 5, 7, 8, 9, 12, 13)

AnswerThe four variable k-map of the given expression is:

The grouping is also shown in the diagram. Hence we get,

F(A, B, C, D) = C' + A'BD

5. Simplify F(A, B, C) = Σ (0, 2, 4, 5, 6) into Product of Sums.

AnswerThe three variable k-map of the given expression is:

The 0's are grouped to get the F'.

F' = A'C + BC

Complementing both sides and using DeMorgan's theorem we get F,

F = (A + C')(B' + C')

6. The simplified expression obtained by using k-map method is unique. True or False. Explain your answer.

Answer

False. The simplest form obtained is not necessarily unique as grouping can be made in different ways.

7. Give the characteristic tables of RS, JK, D and T flip-flops.

AnswerRS flip-flop.

JK flip-flop

J | K | Q(t+1) |

0 | 0 | Q(t) |

0 | 1 | 0 |

1 | 0 | 1 |

1 | 1 | Q'(t) |

D flip-flop

T flip-flop

8. Give excitation tables of RS, JK, D and T flip-flops.

AnswerRS flip-flop.

Q(t) | Q(t+1) | S | R |

0 | 0 | 0 | X |

0 | 1 | 1 | 0 |

1 | 0 | 0 | 1 |

1 | 1 | X | 0 |

JK flip-flop

Q(t) | Q(t+1) | J | K |

0 | 0 | 0 | X |

0 | 1 | 1 | X |

1 | 0 | X | 1 |

1 | 1 | X | 0 |

D flip-flop

T flip-flop

9. Design a BCD counter with JK flip-flops

Answer

10. Design a counter with the following binary sequence 0, 1, 9, 3, 2, 8, 4 and repeat. Use T flip-flops.

Answer

## 2 Comments:

Hi

I read this post two times.

I like it so much, please try to keep posting.

Let me introduce other material that may be good for our community.

Source: Behavioral interview questions

Best regards

Henry

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