Astable multivibrator behavior — which statement best describes its output? Choose the accurate description of an astable circuit's output state over time.
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Aconstantly switches between two states
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Bis LOW until a trigger is received
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Cis HIGH until a trigger is received
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Dfloats until triggered
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Estays latched unless reset
Answer
Correct Answer: constantly switches between two states
Explanation
Introduction / Context:An astable multivibrator has no stable state. It continuously oscillates between two levels, generating a periodic waveform without requiring external triggers. This question verifies recognition of astable behavior compared to mono- and bi-stable types.
Given Data / Assumptions:
- Astable configuration using active components and RC feedback
- Free-running oscillator behavior expected
Concept / Approach:By design, astables perpetually charge and discharge timing capacitors, alternately driving the output HIGH and LOW. No trigger input is required to sustain oscillation, unlike monostables and bistables.
Step-by-Step Reasoning:
Identify presence of any stable resting state: none in an astable.Result: output keeps toggling between logic levels with a period set by R and C.Verification / Alternative check:555 in astable mode or cross-coupled inverters with RC produce a continuous square wave, confirming the description.
Why Other Options Are Wrong:
- LOW until triggered / HIGH until triggered: describes monostable behavior.
- Floats until triggered: outputs are not left floating in proper designs.
- Stays latched unless reset: describes bistable flip-flops.
Common Pitfalls:
- Confusing "needs power-up to start" with "needs a trigger"; many astables self-start due to component tolerances.
Final Answer:constantly switches between two states