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# Ee2 chapter15 multivibrator

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### Ee2 chapter15 multivibrator

1. 1. IT2001PAEngineering Essentials (2/2)Chapter 15 - Multivibrator Lecturer Namelecturer_email@ite.edu.sg Nov 20, 2012Contact Number
2. 2. Chapter 15 - MultivibratorLesson ObjectivesUpon completion of this topic, you should be able to: Explain and demonstrate the function of IC555 in a timer circuit. IT2001PA Engineering Essentials (2/2) 2
3. 3. Chapter 15 - MultivibratorSpecific Objectives Students should be able to :  Describe the characteristics of the 3 basic types of multivibrator :  Astable (free running)  Monostable (one shot) and  Bistable (flip flop)  State their applications.  Identify the IC 555 package.  Identify the following pin functions of the IC 555 :  Trigger (Pin 2), Threshold (Pin 6), Control voltage (Pin 5), Discharge (Pin 7), Output (Pin 3) and Reset (Pin 4) IT2001PA Engineering Essentials (2/2)
4. 4. Chapter 15 - MultivibratorMultivibrator  A multivibrator is a circuit whose outputs are bistate.  The output may be either a Low or High.  Multivibrators can be divided into three groups: - Astable multivibrator (Free-running) - Monostable multivibrator (One shot) - Bistable multivibrator (Flip-Flop) IT2001PA Engineering Essentials (2/2) 4
5. 5. Chapter 15 - MultivibratorAstable Multivibrator Free-running oscillator that O/P ASTABLE outputs a rectangular wave and requires no trigger input.INPUT NO INPUTOUTPUT E.g.: as oscillators, square-wave generators. IT2001PA Engineering Essentials (2/2) 5
6. 6. Chapter 15 - Multivibrator Bistable Multivibrator I/P O/P BISTABLE Has two stable states and will • stay in either one indefinitely.INPUTOUTPUT E.g.: as digital storage register. IT2001PA Engineering Essentials (2/2) 6
7. 7. Chapter 15 - MultivibratorMono Stable Multivibrator I/P O/P MONO STABLE Stable in only one of two voltage levels.INPUT E.g.: as a timer.OUTPUT IT2001PA Engineering Essentials (2/2) 7
8. 8. Chapter 15 - Multivibrator555 IC Timer Two modes of operation; i.e. : • Astable (free-running) multivibrator • Monostable (one-shot) multivibrator. IT2001PA Engineering Essentials (2/2) 8
9. 9. Chapter 15 - MultivibratorFree-running multivibrator 555 Vo Output High Free- Vo Vcc Output Low running mode Output wave form Output oscillators between high and low. The frequency of which is determined by • an external resistor-capacitor network. IT2001PA Engineering Essentials (2/2) 9
10. 10. Chapter 15 - Multivibrator One-shot MultivibratorEi Negative-going Vo Time outputby the is is high determined trigger pulse Ei 555 Vcc circuit, not input pulse One-shot mode Vo 0 A t t 0 A Output wave formOutput voltage is low until a• negative-going trigger pulse is applied to the timer. • Then output switches to high. IT2001PA Engineering Essentials (2/2) 10
11. 11. Chapter 15 - Multivibrator555 Pin Connection Trigger (Pin 2) 1 8 Threshold (Pin 6) R 2 Q1 7 Control voltage (Pin 5) R FF Discharge (Pin 7) S 3 R 6 Output (Pin 3) R Reset (Pin 4) 4 Q2 Ref 5 IT2001PA Engineering Essentials (2/2) 11
12. 12. Chapter 15 - MultivibratorNext Lesson IT2001PA Engineering Essentials (2/2) 12