## Digital Electronics MCQs of Engineering Questions. This mcqs are useful in your university SPPU exams 2020, placements exams, GATE and others all exams.

**Before solving this mcqs i suggest you must read this for better concept.**

1. A binary digit is called a _______

a. Bit

b. Byte

c. Number

d. Character

**Ans: a**

2. A byte corresponds to.

a. 4 bits

b. 8 bits

c. 16 bits

d. 32 bits

**Ans: b**

3. The 5 V level of a digital signal is called a logical 1 or HIGH

a. True

b. False

**Ans: a**

4. The +12V level of a digital signal is also called a logical----------

a. 0 or LOW

b. 0 or HIGH

c. 1 or LOW

d. 1 or HIGH

**Ans: d**

5. Positive logic in logic circuit is one in which

a. Logic 0 and 1 are represented by 0 and positive voltages respectively.

b. Logic 0 and 1 are represented by negative and positive voltages respectively.

c. Logic 0 voltage level is higher than logic 1 voltage level.

d. Logic 0 voltage level is lower than logic 1 voltage level.

**Ans: d**

6. The Boolean expression Y=(AB. ’ is logically equivalent to what single gate?

a. NAND

b. NOR

c. AND

d. OR

**Ans: a**

7. The NAND gate output will be low if the two inputs are

a. 00

b. 01

c. 10

d. 11

**Ans: d**

8. The output of a logic gate is 1 when all its inputs are at logic 0. The gate is either

a. a NAND or an EX-OR

b. an OR or an EX-NOR

c. an AND or an EX-OR

d. a NOR or an EX-NOR

**Ans: d**

9. The NOR gate output will be high if the two inputs are

a. 00

b. 01

c. 10

d. 11

**Ans: a**

10. When an input signal A=11001 is applied to a NOT gate serially, its output signal is

a. 00111

b. 00110

c. 10101

d. 11001

**Ans: b**

11. How many NAND circuits are contained in a 7400 NAND IC?

a. 1

b. 2

c. 4

d. 8

**Ans: c**

12. The AND gates give high output when both inputs are ....?

a. high, high

b. high, low

c. low, high

d. low,low

**Ans: a**

13. The OR gates give low output when both inputs are ....?

a. high, high

b. high, low

c. low, low

d. low,high

**Ans: c**

14. The logic gate that will have HIGH or "1" at its output when any one of its inputs is HIGH is an:

a. OR gate

b. AND gate

c. NOR gate

d. NOT gate

**Ans: a**

15. Exclusive-OR (XOR. logic gate can be constructed from what logic gates?

a. OR gates only

b. AND gates and NOT gates

c. AND gates, OR gates, and NOT gates

d. OR gates and NOT gates

**Ans: c**

16. A NAND gate has:

a. LOW inputs and a LOW output

b. HIGH inputs and a HIGH output

c. LOW inputs and a HIGH output

d. None of the these

**Ans: c**

17. The basic logic gate whose output is the complement of the input is the:

a. OR gate

b. AND gate

c. INVERTER gate

d. Comparator

**Ans: c**

18. What input values will cause an AND logic gate to produce a HIGH output?

a. At least one input is HIGH.

b. At least one input is LOW.

c. All inputs are HIGH.

d. All inputs are LOW.

**Ans: c**

19. The NAND gates give low output when both inputs are ....?

a. low, high

b. high, low

c. high, high

d. low,low

**Ans: c**

20. A XOR gate has inputs A and B and output Y. Then the output equation is

a. Y = A + B

b. Y = AB + A'B

c. AB + AB'

d. AB' + A'B

**Ans: d**

21. In a 3 input NAND gate, the number of states in which output is 1 equals

a. 1

b. 2

c. 3

d. 4

**Ans: a**

22. In a 3 input NOR gate, the number of states in which output is 1 equals

a. 1

b. 2

c. 3

d. 4

**Ans: a**

23. An AND gate has three inputs A,B,C out of total 8 input states,output is 1 in

a. 1 states

b. 2 states

c. 3 states

d. 4 states

**Ans: a**

24. An NOR gate has two inputs A and B, output is 1 if

a. A = 0, B = 0

b. A = 1, B = 0

c. A = 0, B = 0

d. A = 1, B = 1

**Ans: a**

25. The total number of input states for 4 input OR gate is

a. 20

b. 16

c. 12

d. 8

**Ans: b**

26. The gate whose output is LOW if and only if all inputs are HIGH, is

a. NAND

b. NOR

c. OR

d. AND

**Ans: a**

27. A waveform that has just two distinct voltages, such as 0 V and 12 V, is called as -------- signal.

a. AM

b. Analog

c. FM

d. Digital

**Ans: d**

28. The positive logic circuit is one in which

a. Logic 0 and 1 are represented by 0 and positive voltages respectively

b. Logic 0 and 1 are represented by negative and positive voltages respectively

c. Logic 0 voltage level is higher than logic 1 voltage level

d. Logic 0 voltage level is lower than logic 1 voltage level

**Ans: d**

29. IC s are

a. analog

b. digital

c. both analog and digital

d. mostly analog

**Ans: c**

30. A NOT gate has...

a. Two inputs and one output

b. One input and one output

c. One input and two outputs

d. none of above

**Ans: b**