Retriggerable monostable multivibrator — identify what is NOT an inherent characteristic. Select the option that does not generally define retriggerable monostables across families.
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AIt is a dual multivibrator.
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BIt has an active-HIGH reset, which terminates all timing functions.
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CIt has no internal timing resistor.
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Dnone of the above
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EIt extends the pulse if retriggered before timeout.
Answer
Correct Answer: It is a dual multivibrator.
Explanation
Introduction / Context:This item checks whether you can distinguish universal characteristics of retriggerable monostables from package- or family-specific features. The focus is on traits that are always true vs traits that may be true only for particular ICs.
Given Data / Assumptions:
- We consider behavior and construction across common logic families (TTL/CMOS).
- Terms like "dual" can describe a package option, not a fundamental property.
Concept / Approach:Retriggerability describes timing behavior: new triggers extend the active pulse. Whether an IC is "dual" (two monostables per package) or uses a particular reset polarity varies by part number and family. External timing components are also typical and not unique to retriggerable devices.
Step-by-Step Reasoning:
Identify core behavior: retriggering extends the output pulse.Check packaging: "dual" refers to two one-shots in one IC (e.g., certain 74x123 variants), not an inherent property.Reset polarity and internal components vary by manufacturer and subfamily.Verification / Alternative check:Some retriggerable parts are single (one per package), others are dual. Therefore "dual" is not universally characteristic.
Why Other Options Are Wrong:
- Active-HIGH reset: many parts provide a reset; polarity can vary, but a reset that halts timing is characteristic behavior broadly.
- No internal timing resistor: timing typically uses external R and C in both retriggerable and non-retriggerable families.
- Extends the pulse if retriggered: this is the very definition of retriggerable behavior.
- none of the above: incorrect because at least one option (dual) is not inherent.
Common Pitfalls:
- Assuming a datasheet feature of a specific IC is universal to all retriggerables.
Final Answer:It is a dual multivibrator.