Key characteristics of emitter-coupled logic (ECL) Which statement best summarizes the typical features of ECL logic families?

Introduction / Context:
Emitter-coupled logic (ECL) is a bipolar logic family prized for speed in high-frequency systems such as legacy telecom and instrumentation. Recognizing its signature traits helps in technology selection.

Given Data / Assumptions:

• ECL uses differential (emitter-coupled) transistor pairs biased to avoid saturation.
• Common supplies: negative rails (e.g., −5.2 V) with ground as reference.
• Trade-off: speed vs. power consumption.

Concept / Approach:
Avoiding transistor saturation minimizes storage delay, yielding very short propagation times and excellent high-frequency performance. However, constant bias currents result in relatively high static power draw. Many ECL families reference a negative supply to reduce noise coupling.

Step-by-Step Solution:
Identify supply convention: negative voltage operation is common in ECL.Correlate topology to performance: non-saturating differential pairs → high speed.Power implication: constant bias currents → high power consumption.Therefore, the most accurate concise description is option A.

Verification / Alternative check:
Device datasheets show sub-nanosecond delays with quiescent currents significantly higher than CMOS equivalents.

Why Other Options Are Wrong:
Option B: incorrectly claims low power; ECL power is high.Option C: claims slow propagation and high swings—contradictory to ECL's fast, low-swing characteristics.Option D: multiple inaccuracies (ECL is not low power and typically uses negative supply references).

Common Pitfalls:
Assuming ECL is universally better due to speed; in most modern systems, CMOS wins due to power, cost, and integration.

Final Answer:
negative voltage operation, high speed, and high power consumption