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Lecture #8 Multivibrators
Instructor: Dr. Ahmad El-Banna
Faculty of Engineering Department of Electronics and Communications
Su
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GEE336 Electronic Circuits II
© A
hmad
El-B
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Agenda
Introduction
• Monostable, bistable & Astable
Using 555 Timer
Using Op-AMP 2
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INTRODUCTION 3
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Multivibrators types
• Monostable
• Bistable
• Astable
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Multivibrators types..
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MULTIVIBRATORS USING 555 TIMER
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555 timer
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• The 555 timer consists basically of two comparators, a flip-flop, a discharge transistor, and a resistive voltage divider.
• The flip-flop (bistable multivibrator) is a digital device, a two-state device whose output can be at either a high voltage level (set, S) or a low voltage level (reset, R). The state of the output can be changed with proper input signals.
555 Astable
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555 as an astable or free-running multivibrator, which is essentially a square-wave oscillator.
555 Astable..
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The frequency of oscillation & Duty cycle
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Duty cycles of less than 50%
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555 Monostable Multivibrator
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555 Monostable Multivibrator..
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MULTIVIBRATORS USING OP-AMP
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Bistable Circuit and Transfer Characteristic
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Increasing Vi
Decreasing Vi Complete Ch/s
inverting
Bistable with non inverting transfer ch/s
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Feed fraction
Application of bistable as comparator (Schmit-Trigger)
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Astable
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Astable Circuit ..
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Voltage across capacitor:
Monostable circuit
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• For more details, refer to:
• Chapter 16 at T. Floyd, Electronic Devices,9th edition.
• Chapter 13 at Sedra, Microelectronic Circuits, 5th edition.
• The lecture is available online at:
• http://bu.edu.eg/staff/ahmad.elbanna-courses/12884
• For inquires, send to:
• ahmad.elbanna@feng.bu.edu.eg
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