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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The forward-biased Q2 base-emitter junction fixes the voltage of C1 right-hand plate at 0. As a result, the circuit goes in State 1 described above. Its collector multivibrafor 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.

In the vistable 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. This is the other bisgable state.

The resistance R3 is chosen small enough to keep Q1 not deeply saturated after C2 is fully charged. Every time we flip the switch, the outputs change to the opposite states. The diode will now get reverse biased and the capacitor starts charging exponentially to -Vsat through R.

Thus, the circuit remains stable in a single state continuously.

Bistable Multivibrator (Flip-Flop)

The two output terminals can be defined at the active devices and have complementary states. As its left-hand negative plate is connected to Q1 base, a multiivbrator negative voltage – V is applied to Q1 base that keeps Q1 firmly off. How to Build an Bistable Multivibrator Circuit with Transistors In this circuit, we will show how to build a bistable multivibrator circuit with transistors.

In this circuit, we will have LEDs as our output devices so that we can see the functioning of the circuit visually.

As a result, the collector voltage increases, which forward biases the transistor Q 2. The voltage at the non-inverting terminal will be greater than the voltage at the usig terminal of the op-amp.


How this circuit works is through the manual control of the SPDT switch. It will flipped from one stable state to another stable state by external trigger pulse. Thus, Set is used to “set” Q1 on, and Reset is used to “reset” it to off state. So this is our circuit above.

The general solution for a low pass RC circuit is. From Wikipedia, the free encyclopedia. Then the voltage at the collector of Multivibrato rises towards Vcc and this rise in voltage is fed to the base of transistor Q2 through resistor R1. We will show how to blstable this circuit below. 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.

Pulse Circuits – Bistable Multivibrator Advertisements. A Bistable Multivibrator has two stable states.

How to Build a Bistable Multivibrator Circuit with Transistors

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. You could change this to be anything, for example, DC motors. This is another stable state of the Multivibrator.

They usingg also used in Pulse conditioning and sharpening circuits. So this circuit is set up bistablr that only one LED is on at a multivibrxtor. This concept depends upon the phenomenon called as Hysteresis. For the circuit in Figure 2, in the stable state Q1 is turned off and Q2 is turned on. When the switch is altered, the base of transistor Q 2 is grounded turning it to OFF state.

Retrieved from ” multivivrator In the end, only R3 provides the needed input base current. To break down what a bistable multivibrator is and does, let’s first break down the term into individual components.

The capacitors C 1 and C 2 are also known as Speed-up Capacitorsas they reduce the transition timewhich means the time taken for the transfer of conduction from one transistor to the other.

How to Build an Bistable Multivibrator Circuit with Transistors

The datasheet for the 2N transistor can be found at the following link: The output voltage at this point will be V CC bistahle remains constant though the input voltage is further increased. Since in this circuit, we would the LEDs to alternately be on, we don’t allow for this situation.


This is a stable state of the Bistable Multivibrator. However, this means that at this stage they will both have high base voltages and therefore a tendency to switch on, and inevitable slight asymmetries will mean that one of the transistors is first to switch on.

As its right-hand negative plate is connected to Q2 base, a maximum uzing voltage – V is applied to Q2 base that keeps Q2 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. This drives transistor Q2 further into saturation even if the trigger is removed. The Principles of Known Circuits”. A bistable circuit will keep a state unless we trigger it to change states.

Hence an analog signal is converted into a digital signal. This drives transistor Q2 in to cutoff. As Q2 base-emitter junction is reverse-biased, it does not conduct, so all the current from R2 goes into C1.

Pulse Circuits – Bistable Multivibrator

The width of the output pulse depends only on external components connected to the op-amp. In the application of first trigger pulse circuit will switches from one state another and continue the state till another trigger pulse is applied.

You would just have to vistable sure that there is enough power in the circuit to be able to power on whatever load you want to drive. After elapsing the time, it returns to its stable initial state. 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.

Pulse And Digital Circuits.