What is Multivibrator? Astable, Monostable and Bistable Multivibrator Explained.

What is Multivibrator?

The Multivibrator circuits are widely used in electronics. It is the electronics circuit which is used to implement the two state devices like Relaxation Oscillator, Timer and Flip-flops.

Here the two states refers to the two voltage levels of the output. (e.g  0V, and 5V). Many times the two voltage levels are also represented as either logic high (e.g 5V) and logic low. (e.g 0V).

The multivibrators can be classified into three catagories.

  1. Astable Multivibrator
  2. Monostable Multivibrator
  3. Bistable Multivibrator

Astable Multivibrator

The astable multivibrator does not remain stable in any of the two states. And the output of the multivibrator continuously changes between the two states.

The relaxation oscillators are the example of the astable multivibrator.

Monostbale Multivibrator

In monostable multivibrator, the output remains in the one stable state but whenever an external trigger signal is applied, the output momentarily goes into the unstable state. And after some time it comes back into the stable state. The time required to come back into the stable state depends on the passive components like R and C.

This type of multivibrator is used as a timer in many applications.

Bistable Multivibrator

This type of multivibrator has two stable states. The output used to be in any one of the two stable states. And whenever an external trigger signal is applied, the output goes from one stable state to another stable state. If no triggering action is applied thereafter, then it remains in the new stable state.

The bistable multivibrator is one kind of flip-flop circuit.

All the three types of multivibrator can be designed using either op-amp, transistor pairs or 555 timer IC.

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