option 2
saturation.
ECL is fastest among the three because the transistors are used in difference amplifier configuration, in which they are never driven into saturation and thereby the
storage time is eliminated.
The digital logic family which has the lowest propagation delay time is ECL (Lowest propagation delay time is possible in ECL because the transistors are used in
difference amplifier configuration, in which they are never driven into saturation and thereby the storage time is eliminated).
Non-saturated Logic: In Non-saturated Logic, the transistors are not driven into saturation.
(i) Schottky TTL
(ii) Emitter Coupled Logic (ECL)