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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By using this site, you agree to the Terms of Use and Privacy Policy. Switching of state can be done via Set and Reset terminals connected to the bases. Thus C2 restores its charge and prepares for the next State C2 when it will act as a time-setting capacitor.

The output voltage of the switched-off transistor Q1 changes exponentially from low to high since this relatively high resistive output is loaded by a low impedance load capacitor C1. This can occur at startup without external intervention, if R and C are both very small.

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. It has only one stable state.

Unsourced material may be challenged and removed. Pulse And Digital Circuits. Q1 is on and connects the left-hand positive plate of C1 to ground. 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 charging of C2.

The output voltage of the switched-on transistor Q1 changes rapidly from high to low since this low-resistive output is loaded by a high impedance load the series connected capacitor C1 and the high-resistive base resistor R2. It is also known as flip flop multivibrator. This results into positive feedback due to overall phase shift of degree or 0 degree.


Thus C1 restores its charge and prepares for the next State 1 when it will act again as a time-setting capacitor When anr voltage of C1 right-hand plate Q2 base voltage becomes positive and reaches 0. Assume all the capacitors to be discharged at first. Multivibrator circuits are widely used in storing numbers, counting of pulses, synchronization of arithmetic operations and so on.

Since it produced a square wavein contrast to the sine wave generated by most other oscillator circuits of the time, its output contained many harmonics above the fundamental frequency, which could be used for calibrating high frequency radio circuits. Views Read Edit View history. As a result, Q2 gets switched off. In other projects Wikimedia Commons.

These circuits are basically closed loop feedback circuits operating with the feedback.

The capacitor discharges through resistor R and charges astqble to 0. Q2 collector voltage begins falling; this change transfers through the fully charged C2 to Q1 base and Q1 begins cutting off.

It can remain in either of these two states unless an external trigger pulse switches it form one state monosrable the other. In the end, only R3 provides the needed input base current. The width of the output pulse depends only on external components connected to the op-amp. In the monostable configuration, only one of the transistors requires protection.


The general solution for a low pass RC circuit is. One has high voltage while the other has low voltage, except during the brief transitions from one state to the other.

The diode D1 clamps the capacitor to 0. The circuit has two astable unstable states that change alternatively with maximum transition rate because of the “accelerating” positive feedback.


When the circuit is first powered up, neither transistor will be switched on. Applications astable multivibrator applications of multivibrator astable multivibrator bistable multivibrator monostable multivibrator multivibrator types of multivibrator uses of multivibrators. Time bases scanning generators: The astable or free running multivibrator continuously switching from one state to the other and back to the first state.

In practice, oscillation always occurs for practical values of R and C. After elapsing the time, it returns to its stable initial state. When triggered by an input pulse, a monostable multivibrator will switch to its unstable position for a period of time, and then return to its stable state. It has no stable state.

Astable vs Monostable vs Bistable Multivibrator types

A multivibrator is an electronic circuit used to implement a variety of simple two-state [1] [2] blstable devices such as relaxation oscillatorstimers and flip-flops.

If V C is the voltage across the capacitor and from the graph, the time period of the wave formed at capacitor and the output would match, then the time period could be calculated in this way:.

Figure-4 depicts circuit used for bistable multivibrator. It is considered below for the transistor Q1.

multivibrators:astable,monostable and bistable with applications

Wikimedia Commons has media related to Multivibrators. It is also called free running relaxation oscillator. 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. Chaos 22 Monostable Multivibrator Figure-3 depicts circuit used for monostable multivibrator. Multivibrators find applications in a variety of systems where square waves or timed intervals are required.