Q1 a) Prove the Demorgan's laws using Boolean algebra. 
b) Find the minimal sum of product expression for the following Switching function. F (x1, x2, x3, x4, x5) = Sm (1, 2, 3, 6, 8, 9, 14, 17, 24, 25, 26, 27, 30, 31) + Sd(4,5)

Q2 a) describe the working of master-slave JK 
flip flop. State its merit. What is Race problem in flip- flops?

b) Design a negative edge triggered T flip flop. The circuit has two inputs, T(toggle) and 
C(clock) and output Q and Q'. The output state is complemented if T=1 and the clock C changes from 1 to 0. Otherwise under any 
other input condition, the output Q remains unchanged.

Q3 a) Differentiate between: 
i) Combinational and Sequential Logic Circuits.

ii) Synchronous and Asynchronous Counters

Q4 Do 
as directed 
a) Conversion of 100.55 base 10 into binary, octal codes. 
b) Conversion of 1111010011011110 base 2 to decimal, hexadecimal. 

Q5 a) Draw the circuit of a 3 to 8 decoder and describe its operation. How this can 
be used as a DEMUX. b) Design and describe Priority encoder. Digital Electronics 
ASSIGNMENT 'B' 

Q1 A Gray code is a sequence of codes which differ in one bit position at each step. For ex 00, 01, 11, 10, 00 ...is a two-bit Gray code. Design a counter made from JK flip-flops to produce a three-bit Gray code. 
Q2 Mention the various A/D convertors. And Draw and discuss the circuit of a dual scope A/D convertor. Also discuss the comparison of advantages and disadvantages of each of A/D convertor. 
Q3 Draw the circuit of a 4-bit shift registers and describes its operation. Also describe Various different types of shift register with circuit diagram. 

Case Study 
An m: 1 multiplexer has m data inputs; log2m control signals and produces a data output which is equal to the input selected by the control signals. Each different combination of control signals selects a different input. Present an implementation, either as a circuit diagram or as equations, of an 8: 1 multiplexer. Show how 8: 1 multiplexers can be cascaded to build a 64: 1 multiplexer. Digital Electronics 
ASSIGNMENT 'C 

Q1 8421 code is 
a) Self -complementing code 
b) Weighted code 
c) Non-weighted code 
d) Alphanumeric code 
Q2 ASCII code is a 
a) 5-bit code 
b) 7-bit code 
c) 8-bit code 
d) 10-bit code 
Q3 In synchronous counters the clock input of each of the bi-stables are connected together so that each 
changes state at the same time. 
a) True 
b) False 
Q4 Decimal that converts from decimal to binary numbered is called _______________ 
a) Encoder 
b) Decoder 
c) Converter 
d) CPU 
Q5 The binary number 101100.110 in octal number will be a) 
152.6 Digital Electronics 
b) 154.6
c) 145.2 
d) 174.5 
Q6 64 K is ___ . 
a) 6400 
b) 64000 
c) 65536 
d) 64536 
Q7 Binary 1000 will be the result of which of the following 
a) Binary 1000 - 100 
b) Binary 1011 - 1111 
c) Binary 1111 - 111 
d) Binary 11111 - 1111 
Q8 Decimal 14 in binary system can be written as____ 
a) 1111 
b) 1110 
c) 0111 
d) 1100 
Q9 In digital electronics, which of the following voltage levels does not denote logic '0'? 
a. 0 volt b. 0.4 volt 
c. <0.8 volt d. none of the above 
Q10 Aside from the binary system, what other number system is commonly used in digital systems? 
a. decimal b. hexadecimal 
c. scale-of-2 d. none of the above 
Q11 In Boolean algebra the OR function is represented by the '+' sign. 
a) True 
b) False 
Q12 A signal having discrete values is known as 
a) a digital signal Digital Electronics 
b) an analog signalDigital Electronics 
c) a natural signal
d) none of the above 
Q13 How many nibbles count in the number 1111 1110? 
a) 4 
b) 8 
c) 2 
d) 16 
Q14 If 2 in binary system 010 then 6 will be 
a) 011 
b) 0111 
c) 1110 
d) None of the above 
Q15 What is binary equivalent of FC6 is _________ 
a) 1111 1100 0110 
b) 011011001010 
c) None of the above 
d) Both of the above 
Q16 The 2's complement of 100001011 is __________ 
a) 011110101 
b) 001110100 
c) 

d) 001111100 
e) 000110100 
Q17 Which of the following are universal gate: a) Digital Electronics 
AND Digital Electronics 
b) NAND
c) NOR 
d) OR 
Q18 Which logic gate has the following truth table? 

Input Input Output 
A B C 
0 0 1 
0 1 0 
1 0 0 
1 1 0 
a) An exclusive NOR gate. 
b) A two-input AND gate. 
c) A two-input OR gate. 
d) An exclusive OR gate 
Q19 In which gate output is complements of its input: 
a) AND 
b) NOT 
c) NOR 
d) None of the above 
Q20 In the Karnaugh map shown below, which of the loops shown 
represents a legal grouping? 


Digital Electronics 


_ -
**"
^ 
h 
^ 
00 
1
t 

01 CD 

• __ 1 
0 o
v
¥ 
^~-c 
0 

11 1 
1 
" ^ 
^-D 
10 0 
1 l 
0 
a) A 
b) B 
c) C 
d) D 
Q21 How many gate inputs are required to realize the following expression? 
F=(B+C+D)(B+C+E)(A+B+C+E)(F+G) 
a) 14 
b) 15 
c) 16 
d) All the above 
Q22 How many cells present in a 4-variable format? 
a) 16 
b) 8 
c) 32 
d) None of t h
e 
a
b 
o
v 
e Digital Electronics 
Q23 Is in positive logic circuits it is normal to use +5V for true and 0V for false? 
a) True 
b) False 
Q24 A logic circuit that accepts one data input and distributes it over several outputs is known as ____ . 
a) Decoder 
b) DMUX 
c) Priority Encoder 
d) All of the above 
Q25 The below circuit diagram is: 

a) 2-to-4 bit Binary decoder 
b) 4-to-2 bit Binary decoder 
c) 2-to-4 bit Priority decoder 
d) None of the above 
Q26 A full adder can be made by adding ____ . 
a) Two half adder 
b) Two half subtractor 
c) Both a and b 

Digital Electronics 
Q27 Master-Slave J-K flip-flop doesn't solves the race around problem occurs in JK-flip-flop 
a) True 
b) False 
Q28 In a ________ , the output of the last flip-flop is connected back to the input of the first flip- 
flop. 
a) Johnson counter 
b) Ring counter 
c) D-type flip-flop 
d) None of the above 
Q29 How many flip-flops are needed for an 8-bit counter? 
a) Two 
b) Three 
c) Four 
d) Eight 
Q30 Which of the following can be used in Keyboard encoder? 
a) Shift registers 
b) Flip-Flop 
c) Registers 
d) All of the above 
Q31 DAC converts _______ . 
a) Analog to Digital 
b) Digital to Analog 
c) Both a and b 
Q32 (247.36)8 = (?)16 
a) A6.78 
b) A7.78_ 
c) 78.A7 
d) 78.A6 Digital Electronics 
Q33 (3F)16-(5C)16 = ( ______ )16
a) D1 
b) 1D_ 
c) D2 
d) DE 
Q34 An array of flip-flop is also known as ________ . 
a) Counter 
b) D Flip-Flop 
c) Register 
d) All of the above 
Q35 Which of the following are based on digital systems? 
a) Electronic calculator 
b) Voting Machine 
c) Traffic signal 
d) None of the above 
Q36 An OR gate is ENABLED by connecting one of its inputs to logic level____. 
a) 0 
b) 1 
c) 0 or 1 
d) None of the above 
Q37 How many data inputs contains by a 64 output lines decoder? 
a) 64 
b) 6 
c) 2 
d) All of the above 
Q38 A flip-flop with active low preset input will have Q'= _____ when preset is counted to 
low. 
a) 1 
b) 0 
c) 1 and 0 
d) None of the above. Digital Electronics 
Q39 How many maximum possible number of states in a clocked sequential circuit having 6 
Flip-flops? 
a) 32 
b) 64 
c) 16 
d) None of the above 
Q40 A dynamic RAM is fabricated using ______ technology. 
a) CMOS 
b) MOS 
c) CHIP 
d) none