Question 9.37: Briefly describe the advantages and disadvantages of ECL....

Advantages: Since ECL is a non-saturated digital logic, transistors do not saturate. It is possible to achieve propagation delays as low as 1-2 ns. This logic family has the lowest propagation delay of any family and is used mostly in systems requiring very high-speed operation. ECL performs an OR function. A side benefit of ECL operation is that the complementary NOR output is also available.

Disadvantages:The noise immunity and power dissipation of ECL, however, are the worst of all the logic families available. In the absence of storage time associated with saturated transistors, the input and output logic levels are not the same. This makes it impossible to connect the output of one gate into the input of the next. Yet another disadvantage of ECL is its relatively high power dissipation, resulting in a great deal of wasted heat which must be removed to prevent the circuits from overheating. This in turn tends to limit the amount of circuitry that can be integrated into a single chip, increasing system size and cost.