Sample Paper of Digital Electronics

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sample paper of Digital Electronics

Maximum Marks=100

Time taken=3 hours

Instructions : Attempt any Five questions selecting atleast one from each unit.All questions carry twenty marks each.

Unit 1

1. Explain the working of BCD to Seven Segment decoder.

Ans : This type of decoder accepts the BCD code on its input and provides outputs to energize seven-segment display devices in order to produce a decimal readout.

BCD to Seven Segment Decoder

2. (a) Design gray to binary code converters

Ans : The diagram below shows how gray to binary conversion is done through the use of gates.

3. (a) Compare PMOS with NMOS.

Ans : PMOS is much easier to produce than the n-channel device.PMOS has more than twice the ON resistance of an equivalent NMOS of the same geometry.

(b) Explain CMOS characteristics in detail.

Ans : Power Supply Voltage, Logic Voltage Levels, Noise Margins, Fan out and Power Dissipation are some of the CMOS characterisitcs.

Unit 2

3. (a) Explain BCD Adder in detail with suitable diagrams

Ans : The diagram below explains how a 4-bit binary adder is used to add 2 digits.

BCD ADDER

(b) Design full adder using mux.

Ans :

Full adder

4. Explain Universal Shift Register in detail.

Ans : This register can work as SISO, SIPO, PISO, PIPO, Left shift register and Right shift register.

Unit 3

5. Define the following terms : (i) Fan out (ii) Operating Temperature (iii) Noise immunity

Ans : Fan out – It is defined as the maximum number of inputs of the same IC family that a gate can drive withou falling outside the specified voltage.Operating Temperature – It is that temperature over which an IC can function properly. Noise Immunity – It is the resistance of the device to unwanted signals or noise while being operational.

6. (a) What is interfacing?

Ans : The output of a circuit/system should match the input of another circuit that has different electrical characteristics.

(b) Discuss the interfacing between CMOS and TTL.

Ans : TTL devices need a supply voltage of 5 V and CMOS devices need it from 3-15V.In order to interface the two several system requirements have to be met.

Unit 4

7. List the various specifications of D/A converters and explain each of them in detail.

Ans : Accuracy, Offset voltage, Settling time, Linearity, Resolution.

8.Explain PLDs in detail with suitable diagrams.

Ans : PLD stands for programmable Logic Devices