1

Describe the difference
between Analog circuit and Digital circuits.


Analog circuits
 It is circuit in which voltage and current vary
continuously for a given range.
 They can take infinite values for specified its range.
 The examples of analog circuits are signal generators,
radio frequency transmitters and receivers, power supply, speed controller of
electric motors.
Digital
circuits
 It is a switching circuit in which voltage level is
switched from one value to another instantaneously therefore they are also
called as switching circuit.
 The transition time for digital circuit is assumed to
be zero.
 They take finite number of distinct values.
 The examples of digital circuits are flipflops,
counters, shift registers etc.

2

Why digital circuits are
also called as logic circuit?


The digital circuit obeys certain rule of logic circuit
therefore they are also called as logic circuits.

3

Describe the advantages
of Digital circuits over analog circuits


Advantages of Digital circuits over analog
circuits
 Higher precision and accuracy
 More versatile
 It is less affected by noise
 Design procedure is very easy
 Semiconductor memory storage is easy

4

What are the limitations
of Digital circuits?


Limitations of Digital circuits
 When the analog quantities are expressed digitally by
digital approximation it is first converted into digital form then digital
technology can be proceeding.
 The processing time due to this conversion increases
and system becomes more complex.

5

Define : Hybrid system


Hybrid system
 The system in which analog and digital techniques can
be employed is called as hybrid system.

6

What are two different levels
of digital circuits?


The two logic level of digital circuits are : HIGH ( 1 ) and LOW ( 0 ).

7

Define : Positive logic
and Negative logic


Positive logic
 It is a system in which HIGH level is represented by 1
and LOW level is represent by 0.
Negative logic
 It is a system in which HIGH level is represented by 0
and LOW level is represent by 1.

8

How many edges does each
pulse consist of?


Edges of pulse
 Leading edge
 Trailing edge

9

Explain the term : Leading
edge and Trailing edge


Leading edge
 The positive going transition for positive pulse and
negative going transition for negative pulse is known as leading edge.
Trailing edge
 The negative going transition for positive pulse and
positive going transition for negative pulse is known as trailing edge.

10

Define : Rise time and
fall time for a given Pulse


Rise time
 The time taken by pulse to rise from LOW to HIGH is
called as rise time.
 It is also defined as the time taken by pulse to rise
from 10% to 90% of the pulse amplitude.
Fall time
 The time taken by pulse to go from HIGH to LOW is
called as fall time.
 It is also defined as the time taken by pulse to fall
from 90% to 10% of the pulse amplitude.

11

Define : Pulse width


Pulse width
 It is defined as the time between 50% levels on the
rising and falling edges for a given pulse.

12

Define : Periodic
waveform and non – periodic waveform


Periodic waveform
 It is waveform which repeats itself at a regular
interval of time for a give time period.
Nonperiodic waveform
 It is waveform which does not repeat at a regular
interval of time for a give time period.

13

Define : Duty cycle


Duty cycle
 It is defined as the ratio of ON time to the period of
pulse time for a given pulse.
 Duty cycle = ON time pulse width / Period of pulse
= T_{ON} / T

14

Explain the System
design, Logic design and Circuit design.
OR
How the digital system
can be divided?


System design
 It is a process of breaking of overall system into
subsystem and specifies characteristics of each subsystem.
 The system design of digital computer consists of type
of memory units, input – output device and arithmetic units.
Logic design
 It involves how to interconnect basic logic building
blocks to perform specific function.
 The binary addition is done by interconnection of logic
gates and flip – flops is example of logic design.
Circuit design
 It involves interconnection of components such as
diodes, resistors and transistors to form a gate, flip flops.

15

Which are the basic
elements requires for building a digital system?


Basic elements : NOT, OR and AND gates and flip flops

16

Which are the universal
gates? Why


Universal gates
 Any digital circuit can be formulated by using NAND and
NOR gate therefore they are called as universal gates.

17

Explain the term : Adder
circuit, Subtractor circuit, Multiplication circuit and Divider circuit


Adder
 It is a digital circuit which performs addition
function.
Subtractor
 It is a digital circuit which performs subtraction
function.
Multiplexer
 It is a digital circuit which performs multiplication
function.
Divider
 It is a digital circuit which performs division
function.

18

Define : Encoding and
Decoding


Encoding
 It is a process of converting a digital number into
binary number e.g. converting 8 into binary number 1000.
 It is a digital device.
Decoding
 It is a process of converting binary number into digital
number in the form of decimal octal etc.
 Converting binary number 1000 into 8.

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