Non-saturating logic family — avoiding transistor saturation Which logic family is characterized by operation that prevents transistor saturation during switching?

Introduction / Context:
Switching speed is heavily influenced by whether devices enter saturation. When transistors saturate, stored charge must be removed before the device turns off, increasing delay. A logic family that avoids saturation can therefore switch faster at the cost of higher power.

Given Data / Assumptions:

• ECL (Emitter-Coupled Logic) uses differential transistor pairs biased in the active region.
• TTL and IIL are bipolar families that can involve saturation or current-steering differently.
• MOS is a field-effect technology, not a single “family.”

Concept / Approach:
ECL keeps BJTs from saturating by using constant current sources and emitter-coupled pairs. Voltages swing over a small range and never drive the transistors into saturation, minimizing storage delay and enabling very short propagation times. TTL variants (even Schottky TTL) reduce but do not fully eliminate saturation effects; IIL is current-mode but distinct in behavior. MOS refers broadly to PMOS/NMOS/CMOS and does not answer the saturation-specific question for bipolar BJTs.

Step-by-Step Solution:

Verification / Alternative check:
Classic 10K/100K ECL datasheets highlight small-swing, non-saturating characteristics as the source of speed.

Why Other Options Are Wrong:

• TTL: Schottky clamps reduce saturation depth but do not fully avoid it.
• MOS: Not a bipolar family; the question targets bipolar saturation behavior.
• IIL: Uses current injection; not characterized primarily by “no saturation” like ECL.

Common Pitfalls:
Assuming “MOS” implies non-saturation; the concept here is about BJT saturation avoidance.

Final Answer:
ECL