what is multivibrator?
The name mutivibrator designates a group of the circuits widely applied for switching as shift registers or temporary memories and as square were timing oscillator or clocks. These circuits are basically closed loop feedback circuits operating with the feedback.
Types of multivibrators
There are three general types of multivibrators, which are:
- The astable or free running mutivibrator which has no stable states. It continuously switched between two limits without application of an external signal it is a square wave oscillator.
- The monostable or one shot multivibrator: it has one only stable state. It can be switched from stable state to the other, it then returns to the first stable state after a time delay.
- The bistable or flip flop. It has two stable states and can be triggered from one stable state to the other by external signal.
Uses of multivibrators
Some of the uses of multivibrators are:
- They are used as a Frequency dividers
- Used as a sawtooth generators
- They are used as wave and pulse generators
- They are used as standard frequency source
- They are used in radar and tv circuits
- They are also used as a memory elements in computer
What is meant by astable multivibrator ?
The astable or free running multivibrator continuously switching from one state to the other and back to the first state. In other words it switches between two limits without application of an external signal. It is a square of rectangular wave oscillator.
It is also called free running relaxation oscillator.It has no stable state but only has two half stable states between which it oscillating.
In this circuit none of the two transistors reach at stable state.When one transistor is ON the other transistor is OFF and in this way they continuously switch to and fro at a rate depending on RC time constant in circuit.In this way it oscillates and generates pulses.Besides this two outputs of 180º are available.
It has two also two energy storing capacitors.
Applications astable multivibrator
- The astable or free running multivibrator is used as a square wave frequency generator
- As a timing oscillator or clock of a computer system.
- It is also used for a flashing lights, switching and power supply circuits.
What is meant by One shot Or Mono State Multivibrator?
It has only one stable state. It can be switched from stable state to a quasi stable state by an external signal, it then returns to the stable state after a time delay.
It is also known as single shot or one shot multivibrator.Other names of monostable multivibrator are delay multivibrator and unimultivibrator.
It has one absolutely stable state and one quasi stable state.
It can be switched to quasi stable state by an external trigger but it returns to the stable condition after delay time which is determined by the components of circuit.It supplies a single out put pulse of desired duration for every input trigger pulse.
It has one capacitor as energy storing element.
Applications of mono stable multivibrator
- The monostable multivibrator is used as delay and timing circuits.
- It is also used for temporary memories.
- It is often used to trigger another pulse generator.
- It is used for regenerating old and worn out pulses.
What is meant by bistable (flip flop) multivibrator?
It has two stable states and can be triggered from one stable state to the other by an external signal.
It is also known as flip flop multivibrator.It has two stable states.It can remain in either of these two states unless an external trigger pulse switches it form one state to the other.It has no energy storing element.
Bistable multivibrator applications
- The bistable multivibrator or Flip Flop is of great importance in digital operation in computers, digital communications.
- It is also used for reversing to the supply to a given circuit or change supply to two circuit at regular intervals.