Definition of fanout in digital logic families What do we call the maximum number of standard logic inputs that a single gate output can reliably drive without causing logic-level errors?

Introduction / Context:
When interconnecting digital devices, a single output often drives multiple inputs. Each input draws some current (or presents capacitance), and the driving gate has limited sourcing/sinking capability. The term that quantifies “how many loads” can be connected is fundamental to reliable system design.

Given Data / Assumptions:

• A logic family specifies I_OH/I_OL (output current limits) and I_IH/I_IL (input current requirements).
• Fanout is computed separately for HIGH and LOW states in many families.
• Voltages must remain within VIH/VIL thresholds under load to avoid errors.

Concept / Approach:
Fanout is defined as the number of identical inputs that a single output can drive while guaranteeing valid logic levels. Engineers compare the driver’s guaranteed output current to the sum of the receivers’ required input currents to determine maximum loading for both logic states.

Step-by-Step Solution:

Verification / Alternative check:
Classic TTL example: I_OH ≈ −0.4 mA and I_IH ≈ 40 µA → ≈10 loads; I_OL ≈ 16 mA and I_IL ≈ 1.6 mA → ≈10 loads, yielding a fanout of 10.

Why Other Options Are Wrong:

Common Pitfalls:
Ignoring capacitive loading and rise/fall-time degradation—fanout is a DC specification; dynamic performance may limit practical loading further.

Final Answer:
fanout