Chapter 8 Digital Electronics

8/14/2019 Chapter 8 Digital Electronics

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Q.1. Convert fractional decimal number (0.625) to into binary

number.

Ans.

Q. 2. Convert a decimal number (100.625) in binary.

Ans.For integer part:


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Q. 3. What is a truth table ? Why is it so Called?

Ans.Truth table lists the possible outcomes of all inputs to a logic gate. It iscalled so because it always gives true values.

Q. 4. How are analog and digital signals different from each other?

Ans. Analog signals are continuous signals where as digital signals are

discrete signals.

Q.5. Differentiate between positive and negative logic.

Ans.If higher of two voltages is represented by I and lower by 0 the logic is

positive. If lower of two voltages is represented by I and higher by 0, the

logic is negative.

Q6 What is man inverter in digital electronics

Ans .A logjcgate whose output is Inverse of its input is called as inverter


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Q 7. What is meant by radix Or baae of a number system.

Ans. Radix or base of a number system is the number of digits or distinct

symbols used to represent various numbers.

Q.8.What is a flip-flop?

Ans. A flip flop is a basic memory element made up of assembly of logicgates and is used to store I - bit of information.

Q. 9. What is race around condition in J-K flip flop ? What is its truthtable?

Ans.The truth table for J-K flip flop is:

When both inputs are high, the master flip flop is copied by the slave flipflop. It continuous to follow the master. This state is called race around

condition in which continuous set and reset operations are performed.


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Q. 10. What are universal logic gates?

Ans.A logic gate which can perform all mathematical operations is called aslogic gate. For example NAND and NOR gates.

Q.11.What is a latch?

Ans.It is a D-flip flop and stores one bit oL data.

Q. 12. Convert the decimal number (453.75) into hesadecimal.

Ans Integer part


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Q. 13. Convert the decimal number 39.75 to hexadecimal

.Ans.

Q 14 What is the difference between combinational and sequentialcircuit?

Ans.Combinational circuits are formed by combination of various logicgates.

Sequential circuits are formed by having a particular sequence of flip-flops.

Q. 15. Draw symbols of NAND gate and NOR Gate.

Ans.


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Q. 16. Convert (l245) into Binary number system.

Ans.

Q. 17. Convert (4287) into hexadecimal number system.

Ans.

.


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Q. 18. Convert the decimal number (453.75) into hexadecimal.

Q. 19. Give the truth table for J-K flip flop.


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Q. 22. What is XOR gate? Draw its Truth table.

Ans.XOR gate is exclusive-Or gate. The output of this gate is high if and

only if only one input is high the symbol is:


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SHORT ANSWER TYPE QUESTIONS

Q. 1. Convert hexadecimal number 8A 3D into decimal and binaryequivalent. Convert decimal number 5796.12 into hexadecimal.

Q. 2. What are universal gates and why are they so called ? How canOR and XOR gate be realized using NAND gates only?

Ans.Universal gates are those which can perform all basic logicaloperations. They are so called because all other gates can be realised usingthese gates. Examples are NAND and NOR gates:


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Q. 3. Perform following operations using 9s and 10s complement.


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Q. 4.Perform following using ls complement.


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Q. 5. Perform using 2s complement.

Q. 6. What are advantages of use of binary numbers in digital

computers?

Ans.Binary numbers have numerous advantages in digital computers someof them are:

(i) An ordinary switch has .two stages which can easily be represented by

binary numbers.(ii) When a current flows through a wire, magnetic flux is created. Directionof flux is either positive (inward) or negative (outward). This can be easily

represented by binary logic.(iii) A card with punched holes represents two states similar to

binary system.(iv) Transistors are also two state devices and hence their representation

can be done using binary number system.


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Q. 7. What are signed binary numbers ? How subtraction of binary

numbers is carried out in 2s complement representation?

Ans.Signed binary numbers carry signs +ve or - ye to the binary number.

For carrying out subtraction of binary number using 2s complement, wefollow following steps

(i) We take 2s complement of number to be subtracted, Add it to thenumber from which subtraction was to be performed.

(ii) We check the result if end carry occurs it is discarded and a ye signreplaces +ve. If end carry does not occur, we take 2s complement of result

and place a ye sign before it.

Q. 8. What are the different logic gates? Give their truth tables.

Ans.Different logic gates are:1. OR Gate


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Q. 9. Give the logic diagram of clocked RS flip flop. Discuss its

working.

Ans.Logic diagram of clocked R - S


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When the clock signal is low, the flip flop does not give high, the flip flops

gives the output.The truth table is as shown below:

Chapter 8 Digital Electronics

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