 Multivibrators

 §  Multivibrator

•      Multivibrators are a group of circuits which have two states i.e. ON state and OFF state.

•      They produce different types of waveforms such as square wave, rectangular wave, pulses etc.

•      There are three types of multivibrator:

•      1) Astable multivibrator or free running multivibrator

•      2) Monostable multivibrator or one shot multivibrator

•      3) Bistable multivibrator or flip flop

  • Astable multivibrator or free running multivibrator

•      In astable multivibrator, the two states of the circuit are momentarily stable and circuit switches respectively between these two states.

•      It does not require any external triggering signal and is self sustaining multivibrator.

•      Following fig. shows the output waveform of astable multivibrator.


Fig. Output waveform of astable multivibrator

§  Monostable multivibrator or one shot multivibrator 

•      Monostable multivibrator has only one stable state.

•      This state may be ON (HIGH) or OFF (LOW).

•      It can be made to change these states by applying external trigger pulse, but it remains there for some time.

•      This state is called temporary stable state or quasi-stable state.

•      After some time, it comes to its original state and will remains forever until we do not again trigger to it.

Fig. Output waveform of monostable multivibrator 

§  Bistable multivibrator or flip flop 

§   The bistable multivibrator has two stable states i.e. HIGH (ON) and LOW (OFF)

§  When an external trigger pulse is applied, it changes its state and will remain there till next trigger pulse is applied.

§  The bistable multivibrator remains in its stable state in absence of trigger signal.

                        

    Fig. - Output of bistable multivibrators 


§  Output of multivibrators


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