Multivibrators are the electronic devices having two stage amplifier circuits with positive feedback from the output of one amplifier to the input of the other. It is used in pulse generating, data storing and counting devices. There are three types of multivibrators such as astable multivibrator, monostable multivibrator and bistable multivibrator.

1. PHYSICS
B.Sc. III Sem V (2020-21)

2. “
Dr. Vaishali V. Deshmukh
Assistant professor
Department of physics
Shri Shivaji Science College, Amravati (MS)
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3. 1.
MULTIVIBRATORS
Let’s start with the types of Multivibrators
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4. Switching action of Transistor
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6. What is an multivibrator?
➢ These devices are very useful as pulse generating, storing and
counting circuits.
➢ According to the definition, A Multivibrator is a two-stage resistance
coupled amplifier with positive feedback from the output of one
amplifier to the input of the other.
➢ Two transistors are connected in feedback so that one controls the
state of the other. Hence the ON and OFF states of the whole circuit,
and the time periods for which the transistors are driven into
saturation or cut off are controlled by the conditions of the circuit.
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7. Block diagram of a Multivibrator
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Clock Signal Waveform
Active HIGH – if the state change occurs from a
“LOW” to a “HIGH” on the clock’s pulse rising edge
or during the clock width.
Active LOW – if the state change occurs from a
“HIGH” to a “LOW” on the clock’s pulses falling
edge.
Clock Width – this is the time during which the
value of the clock signal is equal to a logic “1”, or
HIGH.
Clock Period – this is the time between successive
transitions in the same direction, ie, between two
rising or two falling edges.
Duty Cycle – this is the ratio of the clock width to
the clock period.
Clock Frequency – the clock frequency is the
reciprocal of the clock period, frequency = 1/clock
period. ( ƒ = 1/T )

9. Types of Multivibrators
Astable
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11. Transistor Astable Multivibrator
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13. Transistor Monostable Multivibrator
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14. Transistor Bistable Multivibrator
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15. Difference
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1. Astable - It is a free-running multi-vibrator which
does not have any stable states and keeps switching
in between the 2 states due to which square wave
pulses at a fixed frequency are produced.
2. Monostable – It is a 1-shot multi-vibrator which
has only 1 stable state. When an external trigger is
applied, it returns back to its 1st stable state.
3. Bistable – It is a kind of flip-flop which has 2
stable states. It produces a single pulse with a
positive or a negative.

16. Applications
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The astable or free running multivibrator is used as a square wave frequency generator
As a timing oscillator or clock of a computer system.
It is also used for a flashing lights, switching and power supply circuits.
The monostable multivibrator is used as delay and timing circuits.
It is also used for temporary memories.
It is often used to trigger another pulse generator.
It is used for regenerating old and worn out pulses.
The bistable multivibrator or Flip Flop is of great importance in digital operation in
computers, digital communications.
It is also used for reversing to the supply to a given circuit or change supply to two circuit
at regular intervals.

17. Reference books
1. Priciple of Electronics by V. K. Mehta
2. Basic Electronics by B. L. Theraja
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18. “This is my belief: that
through difficulties and
problems God gives us the
opportunity to grow. So
when your hopes and
dreams and goals are
dashed, search among the
wreckage, you may find a
golden opportunity hidden
in the ruins”.
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Dr. A.P.J. Abdul Kalam
(15 Oct 1931 - 27 Jul 2015)

19. Thanks!
Any questions?
You can find me at:
vaishalideshmukh27@gmail.com
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