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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