4000-series CMOS vs. standard TTL — compare speed and power How does the classic 4000-series CMOS logic (operated at 5 V) compare with the standard TTL logic family in terms of switching speed and power dissipation?

Introduction / Context:
When selecting a logic family, designers balance speed, power, and noise margins. Historically, the 4000-series CMOS family became popular for low-power, wide-supply applications, while standard TTL (e.g., 74XX) offered faster switching at the cost of higher static power. Understanding these trade-offs is fundamental in mixed-technology systems and legacy designs.

Given Data / Assumptions:

• Supply near 5 V for both families to allow fair comparison.
• “Standard TTL” refers to classic 74XX, not ALS/HC/HCT variants.
• Propagation delay and quiescent current are the main metrics of interest.

Concept / Approach:
CMOS gates draw negligible static current except during switching, so average power is low for modest frequencies. Classic TTL requires bias currents even when static, so it dissipates more power. However, classic 4000-series CMOS has relatively long propagation delays compared with TTL, especially at 5 V, making it slower in general-purpose speed comparisons.

Step-by-Step Reasoning:

Verification / Alternative check:
Typical data: 4000 CMOS delays in tens to hundreds of nanoseconds; standard TTL often in the 10–30 ns range, with significantly higher ICC. This corroborates the trade-off statement.

Why Other Options Are Wrong:

• “More power” for CMOS: incorrect—CMOS is famed for low power.
• “Faster speed” for 4000 CMOS vs standard TTL: generally false.
• “Equal” ignores well-documented differences.

Common Pitfalls:

• Confusing modern HC/HCT CMOS (faster) with the classic 4000-series.

Final Answer:
less power dissipation and slower speed