Digital fault diagnosis — output short to ground at a driving gate What is the most likely indication observed in a digital system when the output node of a driving logic gate is shorted directly to ground (0 V), considering its fan-out to multiple load gates?

Introduction / Context:
A common hardware fault in digital circuits is a “hard short” from a gate’s output node to ground. Because this node often fans out to several inputs, understanding the observable symptoms helps technicians localize and fix the failure quickly. This question tests practical fault-analysis intuition for TTL/CMOS outputs driving multiple loads.

Given Data / Assumptions:

• The driving gate's output pin is shorted to 0 V.
• Downstream devices receive this node as their input (fan-out > 1).
• Standard logic thresholds apply; no special wired-OR bus is intended unless explicitly designed.
• No series isolation resistors or current-limiting devices are assumed at the node.

Concept / Approach:
A solid short to ground forces the node to a persistent LOW level regardless of the gate's intended state. Every load input tied to that node now “sees” a LOW. Thus the functional symptom is loss of the intended signal at all of those loads. Side effects can include excessive current draw, heating of the damaged device, and potential logic contention if the system had multiple drivers (which is bad practice outside of wired-logic designs).

Step-by-Step Solution:

Verification / Alternative check:
Measuring the node with an oscilloscope shows a flat line near 0 V regardless of upstream toggling. Disconnecting the short (or isolating the driver) immediately restores the waveform at the node, confirming the diagnosis.

Why Other Options Are Wrong:

• Only defective gate affected: false; all loads on that net are affected.
• Node stuck HIGH: a short to ground forces LOW, not HIGH.
• Stuck either HIGH or LOW: a defined short to ground yields LOW specifically.
• Only nearest load fails: the net is common to all loads, so all are impacted.

Common Pitfalls:

• Confusing “short to ground” with “short to Vcc”.
• Overlooking multiple loads on a single net; failures propagate to every connected input.

Final Answer:
There is a signal loss to all load gates.