Correct AnswerD. When its output impedance is low and the input impedance is high
Quick Explanation
One logic output can drive many logic inputs when the driving gate has low output impedance and the receiving gates have high input impedance. This minimizes loading, so the output voltage remains within valid logic levels even when several inputs are connected.
Detailed Explanation
Concept & Reasoning
Fan-out is limited by the current a logic output can source/sink compared with the input current demanded by each load. A low output impedance behaves like a stiff voltage source, while high input impedance means each receiving gate draws little current. That is the desirable combination for driving multiple gates.
How to Solve It in the Exam
Driver: low Zout; loads: high Zin.
Important Exam PointConnect fan-out questions with loading and valid logic-level margins, not only resistance words.
Related Revision Path
This question sits in the revision path Digital Electronics → Logic Families → Fan-Out and Loading .
