Logic-level parameters across families: Is it correct that digital IC families specify four logic-level parameters: VIL, VIH, VOL, and VOH?
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ACorrect
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BIncorrect
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COnly correct for TTL, not CMOS
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DOnly correct for ECL, not TTL/CMOS
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E
Answer
Correct Answer: Correct
Explanation
Introduction / Context:Understanding logic-level thresholds and output drive limits is fundamental for interfacing between IC families. Standard datasheet parameters define input recognition levels and guaranteed output levels for logic 0 and logic 1. This question checks familiarity with those four canonical parameters.
Given Data / Assumptions:
- VIL and VIH are input-level thresholds defining recognized LOW and HIGH ranges.
- VOL and VOH are guaranteed output voltage levels for LOW and HIGH outputs under specified load.
- Applies to TTL, CMOS, and other families with different numeric values.
Concept / Approach:Datasheets nearly always present VIL, VIH, VOL, and VOH. Designers ensure margin by comparing an output's VOL/VOH against the next stage's VIL/VIH. While the numeric values differ (for example, TTL vs. CMOS vs. LVCMOS), the categories remain consistent and enable safe logic-level interfacing and noise-margin analysis.
Step-by-Step Solution:
Identify input thresholds: VIL (max LOW input), VIH (min HIGH input).Identify output guarantees: VOL (max LOW output), VOH (min HIGH output).Confirm universality across common logic families.Verification / Alternative check:Any standard datasheet for 74-series TTL or 4000-series CMOS lists these parameters, confirming the statement.
Why Other Options Are Wrong:
Incorrect: Conflicts with standard datasheet conventions.TTL-only or ECL-only claims: These parameters are used widely, not limited to one family.Common Pitfalls:Ignoring load conditions that affect VOL/VOH; always check the test current and supply when comparing levels.
Final Answer:Correct