22320 Digital Techniques Viva Questions with Answers
1)
What is the difference between Latch And Flip-flop?
The difference between latches and Flip-flop is that the latches are
level triggered and flip-flops are edge triggered. In latches level triggered
means that the output of the latches changes as we change the input and edge
triggered means that control signal only changes its state when goes from low
to high or high to low.
2)
What is the binary number system?
The system which has a base 2 is known as the binary system and it
consists of only two digits 0 and 1.
3)
State the De Morgan's Theorem?
De Morgan's Theorem stated two theorems:
1.The complement of a product of two numbers is the sum of the
complements of those numbers.
(A. B)' = A' + B'
2. The complement of the sum of two numbers is equal to the product of
the complement of two numbers.
(A + B)' = A'B'
4) Define Digital System?
Digital systems are the system that processes a discrete or digital
signal.
5)
What is meant by a bit?
Bits are the binary digits like 0 and 1.
6)
What is the best Example of Digital system?
Digital Computer.
7)
How many types of number system are there?
There are four types of number system:
- Decimal
Number System.
- Binary
Number System.
- Octal
Number System.
- Hexadecimal
Number System.
8)
What is a Logic gate?
The basic gates that make up the digital system are called a logic gate.
The circuit that can operate on many binary inputs to perform a particular
logic function is called an electronic circuit.
9)
What are the basic Logic gates?
There are three basic logic gates-
- AND
gate.
- OR
gate.
- NOT
gate.
10)
Which gates are called as Universal gate and what are its advantages?
The Universal gates are NAND and NOR. The advantages of these gates are
that they can be used for any logic calculation.
11)
What are the applications of the octal number system?
The applications of the octal number system are as follows:
- For
the efficient use of microprocessors.
- For
the efficient use of digital circuits.
- It
is used to enter binary data and display of information.
12)
What are the fundamental properties of Boolean algebra?
The basic properties of Boolean algebra are:
- Commutative
Property.
- Associative
Property.
- Distributive
Property.
14)
What is meant by K-Map or Karnaugh Map?
K-Map is a pictorial representation of truth table in which the map is
made up of cells, and each term in this represents the min term or max term of
the function. By this method, we can directly minimize the Boolean function
without following various steps.
15)
Name the two forms of Boolean expression?
The two forms of Boolean expression are:
- Sum
of products (SOP) form.
- The
Product of sum (POS) form.
16)
What are Minterm and Maxterm?
A minterm is called Product of sum because they are the logical AND of
the set of variables and Maxterm are called sum of product because they are the
logical OR of the set of variables.
17)
Write down the Characteristics of Digital ICs?
The characteristics of digital ICs are -
- Propagation
delay.
- Power
Dissipation.
- Fan-in.
- Fan-out.
- Noise
Margin.
18)
What are the limitations of the Karnaugh Map?
The limitations of Karnaugh Map are as follows:
- It
is limited to six variable maps which means more than six variable
involving expressions are not reduced.
- These
are useful for only simplifying Boolean expression which is represented I
standard form.
19)
What are the advantages and disadvantages of the K-Map Method?
The advantages of the K-Map method are as follows-
- It
is an excellent method for simplifying expression up to four variables.
- For
the logical simplification, it gives us a visual method.
- It
is suitable for both SOP and POS forms of reduction.
- It
is more suitable for classroom teachings on logic simplification.
The disadvantages of the K-Map method are as follows:
- It
is not suitable when the number of variables exceeds more than four.
- For
Computer reduction, it is not suitable.
- We
have to take while entering the numbers in the cell-like 0, 1 and don't
care terms.
21)
Define Pair, Quad, and Octet?
Pair: Two adjacent cell of karnaugh map is called as Pair. It cancels one
variable in a K-Map simplification.
Quad: A Pair of Four adjacent pairs in a karnaugh map is called a quad. It
cancels two variables in a K-Map simplification.
Octet: A Pair of eight adjacent pair in a karnaugh map is called an octet. It
cancels four variables in a K-map simplification.
22)
Define Fan-in and Fan-out?
Fan-in- The Fan-in of the gate means that the number of inputs that are
connected to the gate without the degradation of the voltage level of the
system.
Fan-out- The Fan-out is the maximum number of same inputs of the same IC
family that a gate can drive maintaining its output levels within the specified
limits.
23)
Write the definition of the Duality Theorem?
Duality Theorem states that we can derive another Boolean expression
with the existing Boolean expression by:
- Changing
OR operation (+ Sign) to AND operation (. Dot Sign) and vice versa.
- Complimenting
0 and 1 in the expression by changing 0 to 1 and 1 to 0 respectively.
24)
What is Half-Adder?
Half-adder is the circuits that perform the addition of two bits. It has
two inputs A and B and two outputs S (sum) and C (carry). It is represented by
XOR logic gate and an AND logic gate.
25)
What is Full-Adder?
Full-adder is the circuits that perform the addition of three bits. It
has three inputs A, B and a carry bit. Full adders are represented with AND, OR
and XOR logic gate.
26)
What is power dissipation?
Period time is the electrical energy used by the logic circuits. It is
expressed in milliwatts or nanowatts.
Power dissipation = Supply voltage * mean current
taken from the supply.
27)
What is a Multiplexer?
The multiplexer is a digital switch which combines all the digital
information from several sources and gives one output.
28)
What are the applications of Multiplexer (MUX)?
The applications of the multiplexer are as follows:
- It
is used as a data selector from many inputs to get one output.
- It
is used as A/D to D/A Converter.
- These
are used in the data acquisition system.
- These
are used in time multiplexing system.
29)
What is a Demultiplexer?
The demultiplexer is a circuit that receives the input on a single line
and transmits this onto 2n possible output line. A Demultiplexer of 2n outputs
has n select lines, which are used to select which output line is to be sent to
the input. The demultiplexer is also called as Data Distributor.
30)
What are the applications of Demultiplexer?
The applications of the demultiplexer are as follows:
- It
is used in the data transmission system with error detection.
- It
is used as a decoder for the conversion of binary to decimal.
- It
is used as a serial to parallel converter.
31)
What are the differences between Combinational Circuits and Sequential
Circuits?
The differences between combinational and sequential circuits are as
follows:
S.No |
Combinational Circuits |
Sequential Circuits |
1. |
These are faster
in speed. |
These are slower. |
2. |
These are easy to
design. |
These are
difficult to design. |
3. |
The clock input
is not required. |
The clock input
is required. |
4. |
In this, the
memory units are not required. |
In this, the
memory units are required to store the previous values of inputs. |
5. |
Example: Mux, Demux, encoder, decoder,
adders, subtractors. |
Example: Shift registers, counters. |
32)
Define Rise Time?
Rise time is the time that is required to change the voltage level from
10% to 90%.
33)
Define fall time?
Fall time is the time that is required to change the voltage level from
90% to 10%.
34)
Define Setup time?
The minimum time that is required to maintain the constant voltage
levels at the excitation inputs of the flip-flop device before the triggering
edge of the clock pulse for the levels to be reliably clocked in the flip flop
is called the Setup time. It is denoted as tsetup.
35)
Define Hold time?
The minimum time at which the voltage level becomes constant after
triggering the clock pulse in order to reliably clock into the flip flop is
called the Hold time. It is denoted by thold.
36)
What is the difference between Synchronous and Asynchronous Counters?
The difference between Synchronous and Asynchronous Counters are as
follows:
S.No |
Asynchronous Counters |
Synchronous Counters |
1. |
These are
low-speed Counters. |
These are
high-speed Counters. |
2. |
The Flip flops of
these counters are not clocked simultaneously. |
In these
counters, the flip-flops are clocked simultaneously. |
3. |
Simple logic
circuits are there for more number of states. |
Complex logic
circuits are there when the number of states increases. |
37)
What are the applications of Flip-Flops?
The applications of flip-flops are:
- Flip-flops
are used as the delay element.
- These
are used for Data transfer.
- Flip-flops
are used in Frequency Division and Counting.
- Flip-Flops
are used as the memory element.
38)
What is the difference between D-latch and D Flip-flop?
D-latch is level sensitive whereas flip-flop is edge sensitive.
Flip-flops are made up of latches.
39)
What are the applications of Buffer?
Applications of buffer are as follows:
- Buffer
helps to introduce small delays.
- Buffer
helps for high Fan-out.
- Buffer
are used to eliminate cross talks.