20/03/2020

Basic of Digital Electronics Interview Question Answer - 1



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 flip-flops, 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
  • Semi-conductor 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.

Non-periodic 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

                = TON / 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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