Multivibrator how does it work

I recommend verifying the things I am writing here by using a simulator. We know from how transistors work that Q1 is only turned ON if it has 0. The right side of the capacitor C2 connects to 9V through R4 and L2, so it is charging and the voltage is rising. A capacitor charges exponentially, which means the voltage rises quickly in the beginning, then slows down more and more.

The voltage reaches V quickly, but from there the voltage rises slowly. But the right side of C1 is also connected to 9V through the resistor R2, which means it is being charged. When the right side of C1 reaches 0. But when Q2 turns on, something interesting happens with the voltages we had over the capacitor C2…. But now that Q2 turns on, the voltage on the right side of C2 is suddenly pulled down to 0V through the transistor. The internal charge of the capacitor does not change though, so the left side keeps being 7.

With So now, the left LED and transistor have turned off. And the right LED and transistor have turned on. The left side of C2 starts at Thus, the circuit has no stable state, and the two states are merely temporary ones termed as quasi-state.

So, a continuous output is generated by performing successive transitions from one state to another after a fixed time duration. It is to be noted here that the time duration of switching between one quasi-state to the other depends on the time constant and other parameters of the circuit. Monostable Multivibrator : As the name here itself is indicating that it has a single stable state and a quasi-state.

Here, out of the two coupling networks, one provides ac coupling and the other provides dc coupling. Thus, providing one stable and one quasi-state. Unlike the astable multivibrator, here, a triggering pulse is required in order to have transition from the stable state to the quasi-state. However, in order to have transition again from quasi-state to a stable state no any triggering pulse is provided.

So, to have a stable state again, a predetermined timing interval is provided as given in case of the astable multivibrator. Thus, after a certain time period decided by the time constant, the circuit comes back to its initial state i.

Bistable multivibrator : A bistable multivibrator has 2 stable states. Here, a separate trigger pulse is required in order to have transition from one stable state to another stable state. Here, only dc coupling is provided by the coupling networks and hence the energy storing element is not required.

When the trigger pulse is first applied, the transistor in the circuit gets cut-off thus showing an off stable state. To fulfill both the conditions the oscillator must have some form of amplifier and a portion of its output must be fed back re-generatively to the input.

If the gain of the amplifier is less than unity, the circuit will not oscillate and if it is greater than unity, the circuit will be over driven and produce a distorted waveform. A simple oscillator can produce sine wave but it cannot generate a square wave. The square wave can be generated by use of multivibrator. A multivibrator is a form of the oscillator which has two stages due to which we can get output by either of the states. It is basically two amplifier circuits arranged with regenerative feedback.

In this, neither of the transistors conducts simultaneously. At a time, only one transistor conducts and another one is in off state. Some circuits have certain states; the state which has fast transition is called switching processes, where there is fast change of current as well as voltage. This switching is termed as triggering.

Hence, we can trigger the circuit internally or externally.