Logic family characteristics — ECL: Evaluate the statement: “Emitter-Coupled Logic (ECL) gates are known for very high frequency capability and small output voltage swing.”

Introduction / Context:
Different logic families trade speed, power, noise margin, and output swing. Emitter-Coupled Logic (ECL) was historically favored for ultra-high-speed systems long before modern CMOS achieved multi-GHz switching. Knowing ECL’s hallmark traits helps in understanding legacy systems and the rationale behind differential low-swing logic families.

Given Data / Assumptions:

• ECL uses differential transistor pairs biased to avoid transistor saturation.
• Outputs are typically small-swing voltage levels around a negative supply (e.g., −5.2 V rails in classic ECL).
• Focus on generic family behavior, not a specific device.

Concept / Approach:
Avoiding saturation minimizes charge storage and thus reduces propagation delay. Small output swings (hundreds of millivolts) further decrease transition time. The combination yields excellent high-frequency performance at the cost of higher static power consumption and tighter termination requirements. Therefore, the statement is accurate and reflects standard ECL properties.

Step-by-Step Solution:

Verification / Alternative check:
Datasheets for classic ECL (e.g., 10K/100K series) show sub-nanosecond propagation delays and output swings about 0.8 V or less, validating the traits asserted in the statement.

Why Other Options Are Wrong:

• Incorrect / below 1 MHz / CMOS hybrids / fan-in dependent: ECL’s speed advantages are intrinsic to its topology, not limited to low frequencies or contingent on CMOS hybrids and simple fan-in counts.

Common Pitfalls:
Equating small swing with low noise immunity without considering controlled terminations and differential routing; overlooking the power cost of always-on bias currents in ECL.

Final Answer:
Correct