ECL is the fastest of all logic families. High speed in ECL is possible…
2017
ECL is the fastest of all logic families. High speed in ECL is possible because transistors are used in difference amplifier configuration, in which they are never driven into ____.
- A.
Race condition
- B.
Saturation
- C.
Delay
- D.
High impedance
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Show answer & explanation
Correct answer: B
Answer: Saturation.
Why this is correct: Emitter-coupled logic (ECL) uses transistors in a differential amplifier/current-steering configuration and deliberately keeps them out of saturation to avoid stored charge that causes slow turn-off.
Saturation introduces excess minority charge carriers in the transistor, producing storage delay when the transistor must turn off.
ECL keeps voltage swings small and steers current so transistors switch between the active region and cutoff rather than entering deep saturation, enabling very fast transitions.
Other terms listed (such as a timing hazard or high impedance) are not the specific transistor operating state that ECL avoids to achieve its high speed.
Bottom line: avoiding saturation minimizes stored charge and storage delay, which is why ECL can achieve very high switching speeds.