Multivibrators

References & Circuit Simulator

Can be downloaded from;

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1. http://elearning.utm.my/22232/
2. https://people.utm.my/rasli1/

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Circuit simulator: Multisim

Observation

• [1]p831-p835
• [2]p732-p750
• [9]p5-32 – p5-37
• [9]p7-1 – p7-33
• [12]p924-p941
• [16]p289
• [17]p477-p488
• [24]p1084-p1108

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Contents

• The purpose
• Multivibrator’s Classification
• Parameters
• Problems/Examples
• Quiz 8
• Multisim Simulation

Purpose

• A MULTIVIBRATOR is an electronic circuit that switches rapidly using positive feedback between two or more states. Its basically a two amplifier circuit and generates square, pulse, triangular waveforms. Also called as nonlinear oscillators or function generators.

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Multivibrator’s Classification

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• Astable multivibrator
• Monostable multivibrator
• Bistable multivibrators
• Integrators
• Differentiators
• Schmitt Trigger
• Voltage Control Oscillator (VCO)
• Phase-Locked Loop (PLL)

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Astable Multivibrators

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• An Astable Multivibrator is the multivibrator with no stable states. Its output oscillates continuously between its two unstable states without the aid of external triggering. The time period of each states are determined by Resistor or Capacitor (RC) time constant or using 555 timer.

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Problems/Examples

Look at given problems;

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-[9]p7-6, example 7.1

-[9]p7-10, example 7.2

-[9]p7-14, example 7.3

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Problems/Examples

Look at given problems;

-[21]p1, example 1

-[21]p2, example 3

-[21]p4, example 5

-[21]p5, example 7

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Monostable Multivibrators

• Monostable multivibrator has one stable state and one quasi stable state (astable state). The output of first stage is given to the second stage and the second stage output is again feedback to the first stage by this the cutoff state will become saturate and saturate state will become to cutoff. Because of the transition of states the multivibrator can be used as oscillators, timers and flip-flops. When an external trigger applied to the circuit, the multivibrator will jump to quasi stable state from stable state. After the period of time it will automatically setback to the stable state, for returning to the stable state multivibrator does not require any external trigger. The time period to returning to stable state circuit is always depends on the passive elements in the circuit (resistor and capacitor values)

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Problems/Examples

Look at given problems;

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-[12]p931, example 21-7

-[12]p941, example 21-12

-[25]p1100, design example 15.9

-[25]p1104, design example 15.10

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Bistable Multivibrators

• The bistable multivibrator has two absolutely stable states. It will remain in whichever state it happens to be until a trigger pulse causes it to switch to the other state. For instance, suppose at any particular instant, transistor Q1 is conducting and transistor Q2 is cut-off. If left to itself, the circuit will stay in this position forever.

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Problems/Examples

Look at given problems;

*[9]p7-19, example 7.4

*[9]p7-22, example 7.5

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Voltage-Controlled Osc (VCO)

• Output frequency can be changed by controlling the input voltage.

Problems/Examples

Look at given problems;

*[12]p935, example 21-9

*[12]p935, practical problem 21-9

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Problems/Examples

Look at given problems;

*[2]p750, problem 17

*[2]p750, problem 18

*[2]p750, problem 19

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Phase-Locked Loop (PLL)

Output frequency can be changed by detecting phase of input signal.

Problems/Examples

Look at given problems;

*[2]p750, problem 20

*[2]p750, problem 21

*[2]p750, problem 22

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Differentiator

• A circuit in which output voltage is directly proportional to the derivative of the input.

Problems/Examples

Look at given problems;

*[17]p486, example 18.5

*[17]p486, example 18.6

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Integrator

• For the integrator circuit of the Figure, the voltage across the capacitor is

Problems/Examples

Look at given problems;

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*[9]p5-32, example 5.17

*[9]p5-34, example 5.18

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Schmitt Trigger

• A Schmitt trigger is a comparator circuit with hysteresis, implemented by applying positive feedback to the non-inverting input of a differential amplifier. It is an active circuit which converts an analog input signal to a digital output signal. The circuit is named a "trigger“ because the output retains its value until the input changes sufficiently to trigger a change.

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Problems/Examples

Look at given problems;

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*[25]p1089, example 15.6

*[25]p1093, example 15.7

*[25]p1097, example 15.8

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Some Important Points on�Multivibrator’s Parameters

• Output frequency, f_o
• Duty Cycle, D
• Pulse Width, W
• Output voltage, V_o
• Duration, T

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Quiz 9

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• [1]p850, problem 20 (Section16-6)
• [1]p850, problem 21 (Section16-6)

Please solve the given problems from particular references.

Quiz 10

• [25]p1132, problem 15.46 (Section15.3)
• [25]p1132, problem 15.47 (Section15.3)

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Please solve the given problems from particular references.

Multisim Simulation 5

-Astable Multivibrator [23]p41

-Monostable Multivibrator [23]p46

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Please solve the given problem using multisim software or related to.

Multisim Simulation 6

-Bistable Multivibrator [23]p51

-Schmitt Trigger [23]p56

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Please solve the given problem using multisim software or related to.

The End�Thanks