if we supply dc input to astable multi vibrator then what will happen??

When you supply a DC input to an astable multivibrator, the circuit will not function as intended. An astable multivibrator is designed to operate in a continuous oscillation mode, generating a square wave output. This behavior relies on the charging and discharging of capacitors, which is fundamentally dependent on alternating current (AC) signals. Let’s break this down further to understand why a DC input disrupts the operation.

Understanding the Astable Multivibrator

An astable multivibrator typically consists of two transistors, resistors, and capacitors. Its primary function is to create a square wave output without requiring any external triggering. The key components involved are:

• Transistors: These act as switches that alternate between on and off states.
• Capacitors: They charge and discharge, which is crucial for creating the oscillation.
• Resistors: They control the timing of the charge and discharge cycles.

How It Works

In a typical operation, the capacitors charge through the resistors until they reach a certain voltage, which turns on one of the transistors. This action causes the other transistor to turn off, allowing the capacitor to discharge through the second transistor. This cycle repeats, creating a continuous square wave output.

The Effect of DC Input

Now, when you apply a DC input to the circuit, the behavior changes dramatically:

• Constant Voltage: A DC input provides a constant voltage level, which means there is no change in voltage to trigger the charging and discharging of the capacitors.
• No Oscillation: Since the capacitors cannot charge and discharge effectively, the transistors will not switch states. This results in a lack of oscillation.
• Potential Damage: If the DC voltage is higher than the rated voltage for the components, it could lead to overheating or damage to the transistors or other parts of the circuit.

Illustrative Example

Imagine the astable multivibrator as a pendulum that swings back and forth. For it to swing, it needs a push (the AC signal) to keep moving. If you were to hold the pendulum still (apply DC), it would not swing at all. Similarly, without the alternating nature of an AC input, the astable multivibrator cannot perform its function of generating a square wave.

Conclusion

In summary, supplying a DC input to an astable multivibrator prevents it from oscillating, as the circuit relies on the dynamic charging and discharging of capacitors to create its output. Therefore, to achieve the desired square wave output, an AC signal or a properly configured input signal that allows for oscillation is essential.