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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This is the output voltage of R 1 C 1 integrating circuit. During State 2Q2 base-emitter junction is forward-biased and capacitor C1 is “hooked” to ground.

It has no stable state but only has two half stable states between which it oscillating. The circuit is usually drawn in a symmetric form as a cross-coupled pair. To approach the needed square waveform, the collector resistors have to be low in resistance. This technique was used in early electronic organs, to keep notes of different octaves accurately in tune.

For example, if Q2 is on and Set is grounded momentarily, this switches Q2 off, and makes Q1 on. The circuit is useful for generating single output pulse of adjustable time duration in response to a triggering signal. Multivibrators find applications in a variety of systems where square waves or timed intervals are required.

Thus, Set is used to “set” Q1 on, and Reset is used to “reset” it to off state. Time bases scanning generators: Hence, when the circuit is switched on, if Q1 is on, its collector is at 0 V.


Toward the emergence of a concepts”. The resistance R3 is chosen small enough to keep Q1 not deeply saturated after C2 is fully charged.

If repeated application of the input pulse maintains the circuit in the unstable state, it is called a retriggerable monostable. By using this site, you agree to the Terms of Use and Privacy Policy. 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.

The circuit has two astable unstable states that change alternatively with maximum transition rate because of the “accelerating” positive feedback.

multivibrators:astable,monostable and bistable with applications

Assume all the capacitors to be monostbale at first. It is also known as flip flop multivibrator. Figure 1, below right, shows bipolar junction transistors. CS1 French-language sources fr Pages with citations lacking titles All articles with failed verification Articles with failed verification from December Articles with failed verification from February Articles needing additional references from January All articles needing additional references Commons category link is on Wikidata.

Now a negative trigger of magnitude V1 is applied to the non-inverting terminal so that the effective signal at this terminal is less than 0. Accordingly, one fully charged capacitor discharges reverse charges slowly thus converting the time into an exponentially changing voltage. It is also called free running relaxation oscillator. A diode D1 clamps the capacitor voltage to 0.


It is a predecessor of the Eccles-Jordan trigger [7] which was derived from the circuit a year later.


Each amplifier stage provides phase shift of degree in midband. It is considered below for the transistor Q1. This results into positive feedback due to monsotable phase shift of degree or 0 degree. This will quickly put the circuit into one of the above states, and oscillation will ensue.

From Wikipedia, the free encyclopedia. Leave a Reply Cancel reply Your email address will not be published. In this way it oscillates and generates pulses. 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 Figure 1. The circuit operation is based on the fact that the asgable base-emitter junction of the switched-on bipolar transistor can provide a path for the capacitor restoration.

This circuit does not oscillate. As a result, the circuit goes in State 1 described above.

Bistable Multivibrator Figure-4 depicts circuit used for bistable multivibrator. When the voltage of C1 right-hand plate Q2 base voltage becomes positive and reaches 0. A free-running multivibrator with a frequency of one-half to one-tenth of the reference frequency would accurately lock to the reference frequency.

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