Circuit of a bistable Multivibrator using two NPN transistor is shown in figure it have two identical transistors Q1 and Q2 with equal collector. Figure (a) shows the circuit of a bistable multivibrator using two NPN transistors. Here the output of a transistor Q2 ‚Äčis coupled put of a transistor Q1 through a. as the bistable multivibrator or Eccles-fordan flip-flop circuit, has found widespread . the other. Using, with a certain safety margin, the smallest possible trigger.

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Now, if this stable state has to be changed again, then either a negative trigger pulse at transistor Q 2 or a positive trigger pulse at transistor Q 1 is applied. If repeated application of the input pulse maintains the circuit in the unstable state, it is called a retriggerable monostable. 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 main difference in the construction of this circuit is that the coupling from the output C 2 of the second transistor to the base B1 of the first transistor is missing and that feedback is obtained now through the resistor R e.

For example, if Q2 is on and Set is grounded momentarily, this switches Q2 off, and makes Q1 on. Suppose transistor Q1 conducts more and it drives in to saturation mode. Views Read Edit View history. And as far as modifications to be done to the circuit, you don’t have to have LEDs as the output devices.

Schmitt trigger circuits are used as Amplitude Comparator and Squaring Circuit. It does not keep any state permanently. Now, the capacitor C2 is fully charged in the previous State 1 to the power supply voltage V with the polarity shown in Figure 1. It continues in that state, unless an external trigger pulse is given. You could change this to be anything, for example, DC motors.


A multivibrator is an electronic circuit used to implement a variety of simple two-state [1] [2] [3] devices such as relaxation oscillatorsmultivbrator and flip-flops. And this is how a bistable multivibrator circuit can be built with transistors. Two transistors are connected in feedback with two resistors, having one collector connected to the base of the other.

As its left-hand negative plate is connected to Q1 base, a multivibraator negative voltage – V is applied to Q1 base that keeps Q1 firmly off. When the voltage of C1 right-hand plate Q2 base voltage becomes positive and reaches 0.


Suppose a positive trigger multivinrator is applied to the base of transistor Q2 through capacitor C2. They can be modified somewhat but should be kept somewhat low. The transistor Q 1 is given a trigger input at the base through the capacitor C 3 and the transistor Q 2 is given a trigger input at its base through the capacitor C 4.

This switch allows us to switch logic states of the outputs. January Learn how and when to remove this template message. In other projects Wikimedia Commons. For this reason Abraham and Bloch called it a multivibrateur. This is the second stable state of the Multivibrator. Accordingly, one fully charged capacitor discharges reverse charges slowly thus converting the time into an exponentially changing voltage.

The multivlbrator of the output pulse depends only on external components connected to the op-amp. When the switch is altered, the base of transistor Q jultivibrator is grounded turning it to OFF state. And if both bisfable were grounded at the same time, both LEDs would be on.

Therefore, we keep it at 9V.

Now this voltage gets applied at the emitter of Q 1. So it is astable, without stability.

How to Build an Bistable Multivibrator Circuit with Transistors

It explains that the output values depends upon both the present and the past values of the input. Bistable Multivibrators are used in applications such as pulse generation and digital operations like counting and storing of binary information. In the end, only Multlvibrator provides the needed input base current. How this circuit works is through the manual control of the SPDT switch.

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The diode will now get reverse biased and the capacitor starts multivigrator exponentially to -Vsat through R.

After elapsing the time, it returns to its stable initial state. The output voltage at this point will be V CC and remains multivibratot though the input voltage is further increased. The datasheet for the 2N transistor can be found at the following link: Every time the switch is changed, each of the LEDs change to the output logic state.

If we adjust the mutlivibrator, the outputs for each of the transistors switches to the output state. This is the first stable state of the Multivibrator.

This latch circuit is similar to an astable multivibrator, except that there is no charge or discharge time, due to the absence of capacitors. Hence an analog signal is converted into a digital signal. A diode D1 clamps the capacitor voltage to 0. Other applications included early television systems, where the various line and frame frequencies were kept synchronized by pulses included in the video signal.

Please help improve this section by adding citations to reliable sources. An astable multivibrator can be synchronized to an external chain of pulses.

Bistable Multivibrator (Flip-Flop)

So the heart of the circuit is alternately grounding the bases of the transistors. This rise in voltage is coupled to the input of transistor Q1 and this makes transistor Q1 further saturated. The Principles of Known Circuits”. Since transistors cannot conduct unless the base receives sufficient power, if we ground the bases, we turn off the transistors.

This technique was used in early electronic organs, to keep notes of different octaves accurately in tune.