Electronics Circuits – Multivibrator


  • Astable multi-vibrator is a simple two state (S1,S2) small electronics device.
  • Its contains two amplifying transistor and cross coupled by resistors or capacitors.
  • During the world was 1, invented the first multivibrator circuit, that is astable multivibrator oscillator, by Henri Abraham (Below Image) and Eugene Bloch during World War I.
Henri Abraham
  • Why called multivibrator
    • its output waveform was rich in harmonics, So its called multi vibrator.

Multi-vibrator Applicaion

  • Its used in timers, relaxation oscillator and flip-flops.
  • Square wave generator
  • Timed interval application

Type of Multi-Vibrators


  • Astable multi-vibrator – .
  • Mono stable multi-vibrator.
  • bi stable multi-vibrator.


Basic Astable Multivibrator



This following two states are simultaneously changing every-time C1, C2 charge and discharge.

  • State 1 : Q1 is switched ON, Q2 is switched OFF.
  • State 2 : Q1 is switched OFF, Q2 is switched ON.




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