Digital logic families – Match each logic family to its characteristic strength List I (Logic family) A. RTL (Resistor–Transistor Logic) B. CMOS (Complementary MOS) C. I2L (Integrated Injection Logic) D. ECL (Emitter-Coupled Logic) List II (Characteristic) High fan-out capability (many loads) Highest speed of operation High noise immunity Lowest power–delay product Select the correct mapping.

Introduction / Context:
Different logic families occupy distinct corners of the speed–power–noise trade space. Recognizing their hallmark advantages is essential when choosing logic for speed-critical or ultra-low-power designs.

Given Data / Assumptions:

• RTL is early-generation logic with relatively low noise immunity and speed.
• CMOS provides very low static power, excellent noise margins, and the industry’s best power–delay product.
• I2L emphasizes high density and very large fan-out with low power (at modest speeds).
• ECL is renowned for the highest speed among classic families due to differential operation and avoiding transistor saturation.

Concept / Approach:

Match each family to its most representative attribute: CMOS → lowest power–delay product; ECL → highest speed; I2L → high fan-out; RTL → among the listed traits, it best aligns with relatively higher noise margins than RTL’s other strengths? Here, we use RTL → 3 only to complete the mapping with the provided four distinct features, while emphasizing that in practice CMOS dominates noise immunity today.

Step-by-Step Solution:

Verification / Alternative check:

Standard digital design texts cite ECL as the fastest, CMOS as lowest PDP with strong noise margins, and I2L for very high fan-out at low power.

Why Other Options Are Wrong:

Pairing “highest speed” with CMOS or I2L ignores ECL’s edge; assigning “lowest PDP” to RTL is incorrect for modern CMOS comparisons.

Common Pitfalls:

Conflating fan-out with noise immunity, and overlooking that ECL’s power consumption is higher despite its speed advantage.

Final Answer:

A-3, B-4, C-1, D-2.