Which logic family is the fastest of all logic families?

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Question

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ALP CBT 2 Electronic Mechanic Previous Paper: Held on 21 Jan 2019 Shift 1

Answer 1

Emitter-coupled-logic (ECL):

Emitter-coupled-logic (ECL) is a BJT logic family that is generally considered the fastest logic available.
ECL achieves its high-speed operation by employing a relatively small voltage swing and preventing the transistors from entering the saturation region. (Reduces the storage delay time).
ECL transistor uses differential amplifier configuration as shown:

Logic Family	Full Name	Advantages	Disadvantages
CMOS	Complementary metal-oxide-semiconductor	1) Lowest power consumption 2) Used in all microcomputer chips today. 3) Most common logic family.	Easily damaged by static discharge and voltage spikes.
TTL	Transistor-transistor logic	1) Earliest developed. 2) Most rugged. 3) Least susceptible to electrical damage.	Consumes more power than CMOS – not suitable for battery-operated devices.
ECL	Emitter-coupled logic	Fastest available logic family	Consumes more power than CMOS. It requires extreme care in the wiring.