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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Q2 is on and connects the right-hand positive plate of C2 to ground.


This is shown in the figure Thus the initial input change circulates along the feedback loop and grows in an avalanche-like manner until finally Q1 switches off and Q2 switches on. Accordingly, one fully charged capacitor discharges reverse charges slowly thus converting the time into an exponentially changing voltage.

It is implemented by the coupling capacitors that instantly transfer voltage changes because the voltage across a capacitor cannot suddenly change. It is basically a switching circuit which generates non-sinusoidal waves such as square, sawtooth and rectangular etc.

As a result, the circuit goes in State 1 described above. Unsourced material may be challenged and removed. Annales de Physique in French. Thus C2 restores its charge and prepares for the next State C2 when it will act as a time-setting capacitor. Operational Amplifiers, 2nd Ed.


In this configuration, one coupling network provides AC coupling while the other provides DC coupling. This can occur at startup without external intervention, if R and C are both very small. During State 2Q2 base-emitter junction is forward-biased and capacitor C1 is “hooked” to monostahle.

Its collector voltage begins rising; this change transfers back through the almost empty C1 to Q2 base and makes Q2 conduct more thus sustaining the initial input impact on Q2 base.

Retrieved from ” https: In practice, oscillation always occurs for practical values of R and C.

It has only one stable state. In other projects Wikimedia Commons. It has no stable state but only has two half stable states between which it oscillating. In the beginning, the capacitor C1 is fully charged in the previous State 2 to the power supply voltage V with the polarity shown in Astabpe 1. As Q2 base-emitter junction is reverse-biased, it does not conduct, so all the current from R2 goes into C1. When the circuit is first powered up, neither transistor will be switched on.

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Multivibrator – Wikipedia

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 next state. For example, if Q2 is on and Set is grounded momentarily, this switches Q2 off, and makes Q1 on.

Views Read Edit View history. Hence, when the circuit is switched on, if Q1 is on, its collector is at 0 V. In the bistable multivibrator, both resistive-capacitive networks C 1 -R 2 and C 2 -R 3 in Figure 1 are replaced by resistive networks just resistors or direct coupling. In this configuration, both coupling networks provide AC coupling through coupling capacitors.


It is a square of rectangular wave oscillator. Please help improve this section by adding citations to reliable sources.

For example, before the ans of low-cost integrated circuits, chains of multivibrators found use as frequency dividers. A single pair of active devices can be used to divide a reference by a large ratio, however, the stability of the technique is poor owing to the variability of the power supply and the circuit elements. The pulse width T of a monostable multivibrator is calculated as follows: In other words it switches between two limits without application of an external signal.

In this circuit, both coupling networks provide DC coupling and no ane storage element is used.

Astable vs Monostable vs Bistable Multivibrator types

In this circuit none of the two transistors reach at stable state. The diode will now get reverse biased and the capacitor starts charging exponentially to -Vsat through R. It is considered below for the transistor Q1. It is also known as flip flop multivibrator.