TTL output current specification: Evaluate — “The maximum current for a LOW output on a standard TTL gate is 100 µA.”

Introduction / Context:
Understanding TTL output drive is crucial for reliable interfacing. Standard TTL can sink substantial current in the LOW state, which defines its fan-out capability. The claim of only 100 µA is drastically lower than actual specifications and would imply almost no fan-out.

Given Data / Assumptions:

• Standard TTL IOL(max) is typically on the order of 16 mA for a logic LOW.
• TTL input LOW current (IIL) per input is around 1.6 mA in classic TTL.
• Fan-out ≈ IOL/IIL ≈ 10 for LOW state.

Concept / Approach:
If a TTL output LOW could only sink 100 µA, it would barely drive a single TTL input (which might demand around 1.6 mA). Actual TTL data contradicts this; therefore the statement is incorrect by more than an order of magnitude.

Step-by-Step Solution:

Verification / Alternative check:
Referencing vendor datasheets for 7400 family confirms typical sink capability and corresponding loading calculations.

Why Other Options Are Wrong:

• Correct / temperature-only / open-collector caveats: None reconcile the large discrepancy with standard specs; open-collector capability is determined by sink current and pull-up, not “no load.”

Common Pitfalls:
Confusing input current with output current; misreading µA vs. mA; using LS/ALS/HCT values without understanding the order of magnitude.

Final Answer:
Incorrect