3 March 2020

Multivibrator Interview Short Question


1
What is meaning of the switching transistor?


Switching transistor
  • When a transistor is used as switch, it is called as switching transistor.


2
Give reason : The transistor has high efficiency as a switch in the OFF and Saturation condition.


Transistor OFF state
  • The collector leakage current flow through transistor during its OFF state therefore the power loss is small as compared to full load current. 
  • Due to this reason, its efficiency is high during OFF state.

Transistor saturation state
  • The power loss during saturation condition is quite low because of small knee voltage.


3
At which state the transistor operates like switch?


Transistor as switch
Cut off
  • The transistor operates like an open circuit.

Saturation
  • The transistor operates like short circuit. Therefore the transistor operates like switch in the cut off and saturation region.


4
Which is stable region for operation of the transistor?


Active region

5
What is meaning of the multi - vibrator?


Multi – vibrator
  • It is an electronic circuit which generates non – sinusoidal waveform.


6
Which type of feedback is used in the multi – vibrator circuit?


Positive feedback

7
How many stages the multi – vibrator consists of?


The multi – vibrator circuit consists of two stage amplifier in which output of the one amplifier feedback to the input of the other amplifier.

8
Which type of waveform the output of the multi – vibrator consists of?


The output of the multi – vibrator should be square or rectangular waveform which depends upon circuit conditions.

9
Describe the different types of multi – vibrator.


Types of multi – vibrator
  • Astable ( Free running )
  • Monostable ( One shot )
  • Bi – stable ( Two shot  or flip flop )


10
Explain the term : Astable multi – vibrator


Astable multi – vibrator
  • It is multi – vibrator in which the operation of two states changes automatically. 
  • However the time of operation of a state depends upon circuit parameters. It is also called as free running multi – vibrator.



Explain the term : Monostable multi – vibrator


Mono stable multi – vibrator
  • It is multi – vibrator which has one stable state and quasi stable i.e. half stable. 
  • One transistor is in ON state whereas the other transistor is in OFF state. 
  • When the input pulse is applied the circuit changes its state. It is also called as one shot multi – vibrator.



Explain the term : Bi – stable multi – vibrator


Bi – stable multi – vibrator
  • It is multi – vibrator which has two stable states. 
  • One pulse is used to generate half cycle of the square wave and another pulse is used to generate next half cycle of the square wave.


11
Which multi – vibrator generates square wave without any external pulse?


Astable or free running multi – vibrator

12
Which multi – vibrator has no stable state?


Astable or free running multi – vibrator

13
Write the expression of frequency for the square wave  Astable  multi – vibrator


Frequency of square wave = 1 / T
                            Where T = 1.4RC

14
Which multi – vibrator has only one stable state?


Monostable multi – vibrator

15
Which multi – vibrator has two stable states?


Bistable multi – vibrator

16
Describe the function of feedback capacitors in the Bistable multi – vibrator.


Function of feedback capacitors
  • To improve the switching characteristics
  • To produce distortion less square wave output





















































































































































































































































































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