Multivibrators — Astable vs. Monostable What is the key operational difference between an astable multivibrator and a monostable multivibrator?

Introduction / Context:
Multivibrators are timing and waveform generation circuits. Understanding their operating modes is fundamental to digital electronics and timing design.

Given Data / Assumptions:

• Compare astable and monostable configurations.
• Assume standard RC timing and comparator thresholds for IC 555 or logic gate equivalents.

Concept / Approach:
An astable multivibrator oscillates continuously without external triggering, generating a periodic waveform. A monostable has one stable state and produces a single pulse when externally triggered, then returns to its stable state.

Step-by-Step Solution:
1) Astable: no stable states; capacitor repeatedly charges and discharges, causing regular toggling.2) Monostable: one stable state; a trigger forces a temporary quasi stable state for a time T = k * R * C, then it returns to the stable state.3) Therefore, the distinguishing feature is free running behavior versus trigger dependent single pulse.

Verification / Alternative check:
Standard texts classify astable as a free running oscillator and monostable as a one shot pulse generator.

Why Other Options Are Wrong:

• The astable needs to be clocked.: Incorrect; it self oscillates.
• The monostable is free running.: Incorrect; it requires a trigger to start the pulse.
• none of the above: Not true since option stating astable is free running is correct.

Common Pitfalls:
Assuming both require triggers; confusing monostable with bistable flip flops.

Final Answer:
The astable is free running.