Important exam oriented question of Digital Logic.
Binary systems
1. Differentiate between Analog and Digital
system. What are the advantages of digital system.
2. What is digital computer? Explain working principle of digital computer
with block diagram.
3. What do you mean by the Gray code? What are its
application?
4. What is decimal code? Differentiate between
BCD and excess-3 code.
5. Explain the error detection code with
example.
6. Convert the following decimal numbers to the indicated bases.
(a) 7562.45 to octal
(b) 1938.257 to hexadecimal
(c) 175.175 to binary
7.Convert the following hexadecimal number to decimal and octal numbers
(a) 0FFF (b) 3FFF
8.Subtract (1010100 - 1000100) using 1’s complement.
9.Using 2’s complement, subtract (1000100-1010100).
Boolean Algebra and Logic Gates
1. State and prove commutative laws,
associative laws and distributive law using logic gate and truth table.
2. What do you mean by Universal gate?
Show that both NAND gate and NOR gate are universal gates.
3. State and prove De-Morgan’s theorem
1st and 2nd with logic gates and truth table.
4. Explain the duality theorem with
example. Simplify the following Boolean
functions to a minimum number of literals: xy + x′z + yz
5. Prove the Boolean expression: AB + AB′C +
A′BC = AB + AC + BC
6. What is logic gate? What are the types of
basic gate.
7. Draw a logic gates that implements the following:
a. F = AB + C D' + B' C
b. F = (A + B) (B' + C) (C' + D + E)
8. Define integrated circuit. What are the characteristics that describe
the performance of IC digital logic families?
Simplification of Boolean Functions
1. Explain the K-map with three variables.
Reduce
the following function using k-map
F = B'D + A'BC' +
AB'C + ABC'
2. What do you mean by K-map? Write
a procedure to reduce K-maps.
3. How do you express the Boolean function as a
product of maxterms? Express the Boolean function F = xy + x′z in a product of
maxterm form.
4. Simplify the Boolean function: F(X,Y,Z) =
∑(0, 2, 4, 5, 6) using three variable K-map.
5. Simplify the Boolean function F = A′B′C′ +
B′CD′ + A′BCD′ + AB′C′ using K-map.
6. Why
don’t care conditions are used? Simplify F(w, x, y, z) = ∑(1, 3, 7, 11, 15)
which has the don’t care conditions d(w, x, y, z) = ∑(0, 2, 5).
7. Describe the forms of Boolean algebra with
example. Define maxterms and minterms.
Combinational Logic
1. What is combinational logic? Design a half
adder logic using only NAND gates.
2. Design the full subtractor circuit with
using Decoder and explain the working principle.
3. What do you mean by full adder and full
subtractor? Design a half subtractor using only NOR gates.
4. Design a full adder with truth table and logic gates.
6. Explain parity generator and checker with suitable example.
7. Describe BCD to excess-3 Code Conversion with truth table and
logic diagram.
8. What is combinational logic?
What are its important features. Design a half adder logic using only NOR gate.
Combination Logic with MSI and LSI
1. What is binary parallel adder? Describe 4-bit binary parallel
adder with logic diagram.
2. What is magnitude comparator?
Design a logic circuit for 4 bit magnitude comparator and explain it.
3. What is decimal adder? Explain it with truth
table and logic diagram.
4. What do you mean by decoder? Design a 3 to 8
line decoder using 2 to 4 line decoder and explain it.
5. Differentiate between a MUX and a DEMUX.
Draw a logic circuit of 8*1 multiplexer.
6. Implement a full-adder circuit with a
decoder and two OR gates.
7. What is encoder? Design a 3 to 8 line
decoder using two 2 to 4 line decoder and explain it.
8. What is demultiplexer? Draw its block
diagram and explain its working principle.
9. Using a decoder and external gates, design
the combinational circuit defined by the following three Boolean functions:
F1 = x′y′z + xz′
F2 = x′yz′ + xy′
F3 = xyz′ + xy
10. Implement the following function Σ (0,1,3,4,8,9,10) using
(a) Decoder
(b) Multiplexer
(c) PLA
11. Differentiate between PAL and
PLA. A combinational circuit is defined by the functions:
F1(A, B,C) = ∑(3, 5, 6, 7)
F2(A, B,C) = ∑(0, 2, 4, 7)
Implement the circuit with a PLA having three
inputs, four product terms, and two outputs.
12. Explain the PLA with the block
diagram. Describe types of ROM in brief.
Synchronous and Asynchronous Sequential Logic
1. Differentiate between combinational logic
and sequential logic. List some applications of sequential logic.
2. What is flip-flop? Mention the application of flip-flop.
3. List the types of flip-flop. Describe
the clocked RS flip-flop.
4. How does a J-K flip flop differs from an S-R
flip flop in its basic operations? Explain.
5. Differentiate between Synchronous Sequential
circuit and Asynchronous Sequential Circuit. What do you mean by D-flip-flop?
6. What is master-slave flip-flop? Explain
master slave J-K flipflop.
7. What do you mean by triggering of flip flop?
Define state table, state diagram and state equation.
8. Explain design Procedure of clocked
Sequential Circuit with suitable example.
9. What is State reduction table? How JK flip
flop can convert into a D-flip flop?
Registers and counters
1. What do you mean by ripple counters? Explain
the 4 bit ripple counter and also draw a timing diagram.
2. What do you mean by shift registers? Mention the
difference types of shift register.
3. What is the difference between a serial and
parallel transfer? Explain how to convert serial data to parallel and parallel
data to serial. What type of register is needed?
4. What do you mean by asynchronous counter? Design the mod-6 asynchronous counter and
explain with truth table.
5. What do you mean by synchronous counter? Design a 3 bit synchronous counter and explain it.
6. What
do you mean by counter? Design a counter as shown in the state diagram below
7. Design the 4-bit synchronous
up/down counter with timing diagram, logic diagram and truth table.
8. Design a 3 bit synchronous counter and
explain it.
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