Download GTU BE/B.Tech 2019 Summer 4th Sem New 2140910 Digital Electronics Question Paper

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GUJARAT TECHNOLOGICAL UNIVERSITY

BE - SEMESTER-IV(NEW) - EXAMINATION - SUMMER 2019

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Subject Code:2140910

Subject Name: Digital Electronics

Time:02:30 PM TO 05:00 PM

Instructions:

1. Attempt all questions.

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2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Q.1

1. Find the XS-3 code of following decimal numbers (i) 26 (ii) 42 (iii) 63 [03 Marks]
2. Differentiate between combinational logic circuit and sequential logic circuit. [04 Marks]

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3. Explain why NAND and NOR are known as universal gates and construct AND, OR and NOT using the universal gates. [07 Marks]

Q.2

1. Convert the following Binary to Gray Code (i)1001 (ii)1010 (iii) 1011 [03 Marks]
2. Convert the following (i) (4CD)₁₆=( )₂ (ii) (26.24)₈= ()₁₀ [04 Marks]
3. Simplify Y=A’BCD’ + BCD’ + BC’D’ + BC’D and implement using NAND gate only. [07 Marks]

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OR

1. State and explain De Morgan’s theorems with truth tables. [03 Marks]
2. Explain minterm and maxterm. [04 Marks]
3. Add 27.125 to -79.625 using 12-bit 2’s complement arithmetic. [07 Marks]

Q.3

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1. Minimize using K-map f(A,B,C,D) = S(1,3,4,6,8,11,15) +d(0,5,7) also draw MSI circuit for the output. [07 Marks]

OR

1. Explain parity checking method of error detection. [03 Marks]
2. Perform the decimal subtraction 206.7-147.8 in 8421 BCD code. [04 Marks]
3. Discuss 4 — bit magnitude comparator in detail. [07 Marks]

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Q.4

1. Explain full adder. [03 Marks]
2. Explain R-2R ladder DAC with necessary diagram. [04 Marks]
3. Draw 4 bit down counter, explain its working with timing diagram and truth table. [07 Marks]

OR

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1. Discuss multiplexer with suitable diagram. [03 Marks]
2. Explain terms Accuracy and settling time for DAC. [04 Marks]
3. Describe 3 to 8 line decoder with logic diagram and truth table. [07 Marks]

Q.5

1. Compare SRAM with DRAM. [03 Marks]

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2. Draw the two input TTL NAND gate circuit with totem pole output. [04 Marks]
3. Describe operation of D/A converter with binary — weighted resistors. [07 Marks]

OR

1. Compare SOP and POS. [03 Marks]
2. Give comparison between EPROM and FLASH memory. [04 Marks]

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3. Describe the working of look-ahead-carry adder. [07 Marks]

Date:13/05/2019

Total Marks: 70

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