The bistable multivibrator has two absolutely stable states. It will remain in Thus diode D​2​ is more reverse-biased compared to diode D1. When the positive. BISTABLE MULTIVIBRATOR CIRCUITS The two types of bistable multivibrator circuits considered here are fixed-bias bistable and self-bias bistable. SELF-BIAS BISTABLE MULTIVIBRATORS In a self-bias bistable multivibrator, the negative VBB source can be removed by including an emitter resistor RE.

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Q2 collector voltage begins falling; this change transfers through the fully charged C2 to Q1 base and Q1 begins cutting off. The diode will now get reverse biased and the capacitor starts charging exponentially to -Vsat through R.

1) Design a fixed-bias bistable multivibrator using Ge transistors

Now, the capacitor C2 is fully charged in the previous State 1 to the power supply voltage V with the polarity shown in Multivigrator 1. Views Read Edit View history. In the end, only R3 provides the needed input base current. It is considered below for the transistor Q1. The transfer characteristics of electronic circuits exhibit a loop called as Hysteresis.

The pulse width T of a monostable multivibrator is calculated as follows: Assume all the capacitors to be discharged at first. As Q2 base-emitter junction is reverse-biased, it does not conduct, so all the current from R2 goes into C1. Accordingly, one fully charged capacitor discharges reverse charges slowly thus converting the time into an exponentially changing voltage. This circuit is simply called as Binary.

Pulse Circuits – Bistable Multivibrator

The Principles of Known Circuits”. 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. This is the output voltage of R 1 C 1 integrating circuit. As the input voltage continues to rise, the voltage at the points C 1 and B 2 continue to fall and E 2 continues to rise.


This section does not cite any sources. 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. bisttable

This is the other stable state. Now the transistor Q 1 will be OFF as the base is grounded. The change of switch to position 2, works as a trigger. This circuit is considered as a special type of its kind for its applications. An astable multivibrator consists of two amplifying stages connected in a positive feedback loop by two capacitive-resistive coupling networks. The output voltage of the switched-off mutlivibrator Q1 changes exponentially from low to high since this relatively high resistive output is loaded by a low impedance load capacitor C1.

This circuit is called as the Regenerative circuit for this has a positive biad and no Phase inversion. The same Multivibrators are designed using operational amplifiers and also IC timer circuits, which are discussed in further tutorials. The resistance R3 is chosen small enough to keep Q1 not deeply saturated after C2 is fully charged.

For example, before the advent of low-cost integrated circuits, chains of multivibrators found use as frequency dividers.


This is another stable state of the Multivibrator. When the voltage of C1 right-hand plate Q2 base voltage becomes positive and reaches 0. In the monostable multivibrator, one resistive-capacitive network C 2 -R 3 in Figure 1 is replaced by a resistive network just multivibrahor resistor. This is a stable state of the Bistable Multivibrator. In practice, oscillation always occurs for practical values of R and C.

The forward-biased Q2 base-emitter junction fixes the voltage of C1 right-hand plate at 0. If repeated application of the input pulse maintains the circuit in the unstable state, it is called a retriggerable monostable.


Similarly, Q2 remains on continuously, if it happens to get switched on first. Thus, Set is used to “set” Q1 on, and Reset is used to “reset” it to off state.

Toward the emergence of a multivibrato. 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 in excess of the V eb breakdown voltage, typically around volts for general purpose silicon transistors.

The output voltage at this point will be V CC and remains constant though the input voltage is further increased. Mutivibrator consists of two amplifying devices transistorsvacuum tubes or other devices cross-coupled by resistors or capacitors. As its left-hand multivibrattor plate is connected to Q1 base, a maximum negative voltage – V is applied to Q1 base that keeps Q1 firmly off. Q2 collector voltage is the output of the circuit in contrast to the astable circuitit has a perfect square waveform since the output is not loaded by the capacitor.

As a result, the circuit goes in State 1 described above. Switching of state can be done via Set and Reset terminals connected to the bases. By using this site, you agree to the Terms of Use and Privacy Policy. If V C is the voltage across the capacitor and from the multivibratoe, the time period of the wave formed at capacitor and the output would match, then the time period bais be calculated in this way:.

The diode D1 clamps the capacitor to 0.