Understanding the Astable Multivibrator: A Key Building Block in Electronics
An Astable Multivibrator is one of the most fundamental and widely used electronic circuits in timing and pulse generation applications. It is a type of oscillator circuit that continuously switches between two unstable states without requiring any external triggering. This self-sustaining behavior allows it to produce a continuous square wave output, making it invaluable in clocks, waveform generators, pulse-width modulation, and other digital systems.
How an Astable Multivibrator Works
The circuit typically consists of two amplifying transistors, resistors, and capacitors connected in a feedback configuration. Unlike monostable or bistable multivibrators, the astable version has no stable state — meaning it constantly alternates between ON and OFF conditions.
Here’s how the process unfolds:
When one transistor switches ON, the other is driven OFF.
The capacitor connected to the OFF transistor begins to charge through a resistor.
Once the capacitor reaches a certain threshold voltage, it triggers the second transistor to switch ON while turning the first one OFF.
This charging and discharging cycle repeats continuously, generating a square wave output.