A multivibrator is a circuit that has two stable states. Each stable state is represented by a voltage e.g 0Volts and 5 volts. The astable variety is when the output. Astable and Monostable Multivibrator Using Timer IC modes: Astable, Monostable and Bistable IC as an astable multivibrator is a. The name mutivibrator designates a group of the circuits widely applied for switching as shift registers or temporary memories and as square.

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Switching of state can be done via Set and Reset terminals connected to the bases. Astaable division ratio of 10, for example, is easy to obtain but not dependable. It has two stable states. The circuit has one stable state and one quasi stable state.

This circuit does not oscillate. The circuit has two astable unstable states that change alternatively with maximum transition rate because of the “accelerating” positive feedback. The first trigger causes conducting transistor to cut-off mode and second trigger causes it back to conducting mode. In this way it oscillates and generates pulses. At the same time, the other empty capacitor quickly charges thus restoring its charge the first capacitor acts as a time-setting capacitor and the second prepares to play this role in the atable state.

It has no energy storing element. The two output terminals can be defined at the active devices and have complementary states. It is implemented by the coupling capacitors that instantly transfer voltage changes because the voltage across a capacitor cannot suddenly change. It is also called free running relaxation oscillator.

This technique was used in early electronic organs, to keep notes of different octaves accurately in tune. It is also known as flip flop multivibrator. It has no stable state. Other names of monostable multivibrator are delay multivibrator and unimultivibrator. This results into positive feedback due to overall phase shift of degree or 0 degree. It astbale a predecessor of the Eccles-Jordan trigger [7] which was derived from the circuit a year later. When triggered by an input pulse, a multivibratoe multivibrator will switch to its unstable position for a period of time, and then return to its stable state.

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Q2 collector voltage begins falling; this change transfers through the fully charged C2 to Multovibrator base and Q1 monostalbe cutting off.

multivibrators:astable,monostable and bistable with applications

Thus C2 astalbe its charge and prepares for the next State C2 when it will act as a time-setting capacitor. From Wikipedia, the free encyclopedia. This is shown in the figure It consists of two amplifying devices transistorsvacuum tubes or other devices cross-coupled by resistors or capacitors.

A multivibrator is basically a two stage RC coupled amplifier with positive feedback from output of one amplifier to the input of the another amplifier. Simultaneously, C1 that is fully discharged and even slightly charged to 0. Other applications included early multivibgator systems, where the various line and frame frequencies were kept synchronized by pulses included in the video signal.

Astable vs Monostable vs Bistable Multivibrator types

The pulse width T of ,onostable monostable multivibrator is calculated as follows: Thus the initial input change circulates along the feedback loop and grows in an avalanche-like manner until finally Q1 switches off monistable Q2 switches on.

Simultaneously, C2 that is fully discharged and even slightly charged to 0. It is considered below for the transistor Q1. These snd are basically closed loop feedback circuits operating with the feedback. Q1 is firmly saturated in the beginning by the “forcing” C2 charging current added to R3 current.

The duration of state 1 low output will be related to the time constant R 2 C 1 as it depends on the charging of C1, and the duration of state 2 high output will be related to the time constant R 3 C 2 as it depends on the bstable of C2.


The resistance R3 is chosen small enough to keep Q1 not deeply saturated after C2 is fully charged. 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. Thus, Set is used to “set” Q1 on, and Reset is used to “reset” it to off state.

To approach the needed square waveform, the collector resistors have to be low in resistance. By using this site, you agree to the Terms of Use and Privacy Policy. In the end, only R3 provides the needed input base current.

During State 2Q2 base-emitter junction is forward-biased and capacitor C1 is “hooked” to ground. Your email address will not be published.

Multivibrator circuits are widely used in storing numbers, counting of pulses, synchronization of arithmetic operations and so on. This is a comparator circuit and hence, the output becomes -V sat. The output voltage has a shape that approximates a square waveform.


While not fundamental to circuit operation, biztable connected in series with the base or emitter of the transistors are required to prevent the base-emitter junction being driven into reverse breakdown when the supply voltage is in excess of the V eb breakdown voltage, typically around volts for general purpose silicon transistors.

It is a square of rectangular wave oscillator. In other projects Wikimedia Commons.