Integrated-injection logic (I²L): Does I²L offer high device density and simpler fabrication compared to TTL, enabling very compact digital circuits?
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AValid — I²L achieves high density and uses simple processes compared to TTL.
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BInvalid — I²L is larger and more complex than TTL.
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CInvalid — I²L is an analog-only technology.
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DValid only when operated above 10 V.
Answer
Correct Answer: Valid — I²L achieves high density and uses simple processes compared to TTL.
Explanation
Introduction / Context:Integrated-injection logic (I²L), also called merged-transistor logic, was designed for very high packing density with low power, competing historically with TTL and ECL in certain applications. This question checks recognition of I²L’s density and process simplicity advantages.
Given Data / Assumptions:
- I²L uses bipolar transistors with current injection for logic operation.
- Low supply voltage and low power consumption.
- Goal: maximize density and simplify fabrication steps.
Concept / Approach:By merging devices and using lateral pnp injectors feeding multiple npn transistors, I²L attains high logic density with fewer processing steps than TTL (which needs multiple diffusions and complex structures). Although slower than the fastest TTL/ECL, I²L’s benefits are area and power.
Step-by-Step Solution:
Identify I²L device structure: injector supplies base current to multiple npn devices.Note minimal device count per gate and small device geometries.Compare to TTL’s multi-emitter input transistor and totem-pole output requiring more complex fabrication.Verification / Alternative check:Historic literature and textbooks highlight I²L’s extremely high gate density and simple process, particularly in early low-power VLSI contexts.
Why Other Options Are Wrong:
- “Larger and more complex” contradicts the design goal of I²L.
- “Analog-only” mischaracterizes a digital logic family.
- “Requires >10 V” is incorrect; I²L uses low supply voltages.
Common Pitfalls:Assuming density always correlates with speed; I²L trades off speed for density and simplicity.
Final Answer:Valid — I²L offers high density with simple fabrication compared to TTL.