Astable and monostable multivibrators are both types of electronic circuits used in generating pulses or waveforms, but they operate differently in terms of their output and behavior.
Astable Multivibrator:
Continuous Oscillation: The astable multivibrator continuously switches between its two unstable states without external triggering. It generates a waveform output that alternates between high and low states, producing a square wave or a similar periodic waveform.
No Stable State: Unlike the monostable multivibrator, the astable multivibrator has no stable state. It oscillates autonomously, creating a continuous output signal without requiring external stimuli or triggers.
No Fixed Duration: As there's no fixed stable state, the pulse widths in the output waveform of an astable multivibrator are not fixed. Instead, they are determined by the circuit components and timing elements.
See the following circuit diagram of astable multivibrator with transistors.
Monostable Multivibrator:
Single Pulse Generation: The monostable multivibrator is triggered externally to produce a single pulse output of fixed duration.
Stable State and Triggered Operation: It has one stable state and switches to an unstable state when triggered by an external signal. After generating a single pulse, it returns to its stable state.
Fixed Pulse Duration: Unlike the astable multivibrator, the monostable multivibrator generates a pulse of fixed duration determined by the circuit's timing components and trigger input.
See the circuit diagram of monostable multivibrator with transistors.
Differences Summarized:
Astable is always oscillating, producing continuous square waveforms, while monostable generates a single pulse in response to an external trigger.
Astable has no stable state, continuously shifting between two states, whereas monostable has one stable state until it's triggered to produce a single pulse.
Astable doesn't require external triggering, while monostable depends on an external trigger to initiate the pulse generation.
In essence, the key difference lies in the continuous oscillation and absence of a stable state in the astable multivibrator, whereas the monostable multivibrator generates a single pulse in response to an external trigger and returns to a stable state afterward.
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