The name mutivibrator designates a group of the circuits widely applied for switching as shift registers or temporary memories and as square. Astable and Monostable Multivibrator Using Timer IC modes: Astable, Monostable and Bistable IC as an astable multivibrator is a. Multivibrator circuits are basically three types- monostable, bistable, astable. Find an examples of each circuit using BJT, logic gates and timer IC.

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Wikimedia Commons has media related to Multivibrators. During State 1Q2 base-emitter junction is reverse-biased and capacitor C1 is “unhooked” from ground. In this circuit, both coupling networks provide DC coupling and no energy storage element is used. Multivibrator circuits are widely used in storing numbers, counting of pulses, synchronization of arithmetic operations and so on.

This can occur at startup without external intervention, if R nonostable C multivivrators both very small. If further trigger pulses do not affect the period, the circuit is a non-retriggerable multivibrator. In this way it oscillates and generates pulses. Multivibartors two output terminals can be defined at the active devices and have complementary states.

In the end, only R3 provides the needed input base current. However, if the circuit is temporarily held with both bases high, for longer than it takes for both capacitors to charge fully, then the circuit will remain in this stable state, with both bases at 0.

A division ratio of 10, for example, is easy to obtain but not dependable. To approach the needed square waveform, the collector resistors have to be low in resistance. Simultaneously, C1 that is fully discharged and even slightly charged to multivibratore.


Astable vs Monostable vs Bistable Multivibrator types

It has two stable states and can be triggered from one stable state to the other by an external signal. In this configuration, one coupling network provides AC coupling while the other provides DC coupling. 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. When the voltage of C1 right-hand plate Q2 base voltage becomes positive and reaches 0.

If repeated application of the input pulse maintains the circuit in the unstable state, it is called a retriggerable monostable. In each state, one transistor is switched on and the bistablle is switched off. Thus C2 restores its charge and prepares for the next State C2 when it will act as a time-setting capacitor.

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

It is also called free running relaxation oscillator. How long this takes is half our multivibrator switching time the other half comes from C1.

Q1 is on and connects the left-hand positive plate of C1 to ground. Multivibrators find applications in a variety of systems where square waves or timed intervals are required.

It can remain in either of these two states unless an external trigger pulse switches it form one state to the other. The voltage at the non-inverting terminal will be greater than the voltage at the inverting terminal of the op-amp.


Each amplifier stage provides phase shift of degree in midband. Electronic oscillators Digital circuits Analog circuits. In other words it switches between two limits without application of an external signal. It is triggered by zero or negative input signal applied to Q2 base with the same success it can be triggered by applying a positive input signal through a resistor to Q1 base.


Figure-4 depicts circuit used for bistable multivibrator. So, the time period of the square wave generated at the output is:.

multivibrators:astable,monostable and bistable with applications

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Leave a Reply Cancel reply Your email address will not be published. As its left-hand negative plate is connected to Q1 base, a maximum negative voltage – V is applied to Q1 base that keeps Q1 firmly off. The first trigger causes conducting transistor to cut-off mode and second trigger causes it back to conducting mode.

Since the circuit vibrates once for a trigger, it is called a uni-vibrator or monostable multivibrator. The general solution for a low pass RC circuit is. While not fundamental to circuit operation, diodes 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 astble excess of the V eb breakdown voltage, typically around volts for general purpose silicon transistors.

Figure-3 depicts circuit used for monostable multivibrator.