Design And Construction Of A Bistable Multivibrator

The Bistable Multivibrators circuit is basically a SR flip-flop. This type of multivibrator circuit passes from one state to the other “only” when a suitable external trigger pulse T is applied and to go through a full “SET-RESET” cycle two triggering pulses are required. Bistable Multivibrators can produce a very short output pulse or a much longer rectangular shaped output whose leading edge rises in time with the externally applied trigger pulse and whose trailing edge is dependent upon a second trigger pulse In bisatble multivibrator, the circuit stays in any one of the two stable states. It continues in that state, unless an external trigger pulse is given. This Multivibrator is also known as Flip-flop. This circuit is simply called as Binary.

TABLE OF CONTENTS

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• AIM OF THE PROJECT
• OBJECTIVE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• APPLICATION OF THE PROJECT
• SCOPE OF THE PROJECT
• DEFINITION OF TERMS
• METHODOLOGY
• PROJECT ORGANISATION

CHAPTER TWO

2.0     LITERATURE REVIEW

2.1     OVERVIEW OF THE STUDY

2.2     HISTORICAL BACKGROUND OF THE STUDY

2.3     OPERATIONAL REVIEW OF BISTABLE

CHAPTER THREE

3.0     CONSTRUCTION METHODOLOGY

3.1     BASICS OF THE SYSTEM

3.2      SYSTEM DIAGRAM

3.3     CIRCUIT DESCRIPTION

3.4     CIRCUIT WITH INTERNAL BLOCK DIAGRAM

3.5      THEORY OF RESISTOR

3.5      THEORY OF CAPACITOR

CHAPTER FOUR

RESULT ANALYSIS

4.0      CONSTRUCTION PROCEDURE

4.1      CASING AND PACKAGING

4.2      ASSEMBLING OF SECTIONS

4.3      TESTING OF SYSTEM OPERATION

4.4     PACKAGING

4.5     MOUNTING PROCEDURE

4.6     RESULT

4.7     COST ANALYSIS

CHAPTER FIVE

5.1      CONCLUSION

5.2      REFERENCES

CHAPTER ONE

1.0                                          INTRODUCTION

1.1                            BACKGROUND OF THE STUDY

A multivibrator is an electronic circuit used to implement a variety of simple two-state devices such as relaxation oscillators, timers and flip-flops. It consists of two amplifying devices (transistors, vacuum tubes or other devices) cross-coupled by resistors or capacitors. The first multivibrator circuit, the astable multivibrator oscillator, was invented by Henri Abraham and Eugene Bloch during World War I.[4][5] They called their circuit a “multivibrator” because its output waveform was rich in harmonics.[6]

There are three types of multivibrator circuits are: Astable multivibrator, Monostable multivibrator and Bistable multivibrator. In this work we are focusing on an astable multivibrator which is the type of multivibrator in which the circuit is stable in either state. It can be flipped from one state to the other by an external trigger pulse. This circuit is also known as a flip-flop. It can store one bit of information, and is widely used in digital logic and computer memory.

Bistable Multivibrators operate in a similar fashion to flip-flops producing one of two stable outputs which are the complement of each other

The Bistable Multivibrator is another type of two state device similar to the Monostable Multivibrator we looked at in the previous tutorial but the difference this time is that BOTH states are stable.

Bistable Multivibrators have TWO stable states (hence the name: “Bi” meaning two) and maintain a given output state indefinitely unless an external trigger is applied forcing it to change state.

The bistable multivibrator can be switched over from one stable state to the other by the application of an external trigger pulse thus, it requires two external trigger pulses before it returns back to its original state. As bistable multivibrators have two stable states they are more commonly known as Latches and Flip-flops for use in sequential type circuits.

The discrete Bistable Multivibrator is a two state non-regenerative device constructed from two cross-coupled transistors operating as “ON-OFF” transistor switches. In each of the two states, one of the transistors is cut-off while the other transistor is in saturation, this means that the bistable circuit is capable of remaining indefinitely in either stable state.

To change the bistable over from one state to the other, the bistable circuit requires a suitable trigger pulse and to go through a full cycle, two triggering pulses, one for each stage are required. Its more common name or term of “flip-flop” relates to the actual operation of the device, as it “flips” into one logic state, remains there and then changes or “flops” back into its first original state.

1.2                        AIM / OBJECTIVE OF THE PROJECT

The main aim of the work is to design a Clock pulse generation circuits that can produce a continuous series of pulses. At the end of this work, this project shall be designed with a predetermined time using transistors.

1.3                                  SCOPE OF THE PROJECT

An astable multivibrator consists of two amplifying stages connected in a positive feedback loop by two capacitive-resistive coupling networks. The amplifying elements are junction or field-effect transistors.

The circuit is usually drawn in a symmetric form as a cross-coupled pair. The two output terminals can be defined at the active devices and have complementary states. One has high voltage while the other has low voltage, except during the brief transitions from one state to the other.

The circuit has two astable (unstable) states that change alternatively with maximum transition rate because of the “accelerating” positive feedback. It is implemented by the coupling capacitors that instantly transfer voltage changes because the voltage across a capacitor cannot suddenly change. In each state, one transistor is switched on and the other is switched off

1.4                         SIGNIFICANACE OF THE PROJECT

The advantages of using a Bistable Multivibrator are as follows −

• Stores the previous output unless disturbed.
• Circuit design is simple

1.5                            LIMITATION OF THE PROJECT

The drawbacks of a Bistable Multivibrator are as follows −

• Two kinds of trigger pulses are required.
• A bit costlier than other Multivibrators.

1.6                          APPLICATIONS OF THE PROJECT

Bistable Multivibrators are used in applications such as pulse generation and digital operations like counting and storing of binary information.

1.7                                   DEFINITION OF TERMS

The following list are terms associated with a timing pulse or waveform.

1. Active HIGH  –  if the state change occurs from a “LOW” to a “HIGH” at the clock’s pulse rising edge or during the clock width.
2. Active LOW  –  if the state change occurs from a “HIGH” to a “LOW” at the clock’s pulses falling edge.
3. Duty Cycle  –  this is the ratio of the clock width to the clock period.
4. Clock Width  –  this is the time during which the value of the clock signal is equal to a logic “1”, or HIGH.
5. Clock Period  –  this is the time between successive transitions in the same direction, ie, between two rising or two falling edges.
6. Clock Frequency  –  the clock frequency is the reciprocal of the clock period, frequency = 1/clock period. ( ƒ = 1/T ).

1.8                                         METHODOLOGY

To achieve the aim and objectives of this work, the following are the steps involved:

1. Study of the previous work on the project so as to improve it efficiency.
2. Draw a block diagram.

• Test for continuity of components and devices,

1. Design and calculation for the device was carried out.
2. Studying of various component used in circuit.
3. Construction of the circuit.

• Finally, the whole device was cased and final test was carried out.

1.9                                                         PROJECT ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.