Logic voltage levels — overlap question: Is it possible (or desirable) to have an overlap between defined HIGH and LOW input voltage ranges in digital logic families?

Introduction / Context:
Digital logic families specify input thresholds: a maximum recognized LOW (VIL(max)) and a minimum recognized HIGH (VIH(min)). A noise margin is created by leaving a forbidden zone between these ranges. The question asks whether overlap is expected or acceptable.

Given Data / Assumptions:

• Properly designed logic specifies VIL(max) < VIH(min).
• Noise margins (NMH, NML) rely on that separation.
• Transient or faulty conditions can momentarily violate these boundaries but are not an intended design feature.

Concept / Approach:
Overlap would mean some voltages are simultaneously considered valid HIGH and valid LOW, which destroys noise immunity and causes indeterminate behavior. Hence, specifications avoid overlap by definition. There can be an undefined region, but not an intentional overlap of valid ranges.

Step-by-Step Solution:

Verification / Alternative check:
Check CMOS logic (e.g., 74HC): typical VIL(max) ≈ 0.3VCC and VIH(min) ≈ 0.7VCC, leaving a clear gap for noise margin.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing undefined regions with overlap; assuming analog noise “makes overlap okay.” It does not—designs must maintain margins.

Final Answer:
Incorrect