A diode characteristic curve is obtained from a plot of current versus voltage. In standard plotting practice, where does this I–V graph begin?

Introduction / Context:
Device I–V curves relate current (vertical axis) and voltage (horizontal axis). For diodes, the curve shows negligible current for reverse bias until breakdown, and an exponential rise for forward bias. Understanding axes and the origin helps interpret operating points correctly.

Given Data / Assumptions:

• Horizontal axis: voltage (V), vertical axis: current (I).
• Origin at (0, 0) denotes zero volts and zero current.
• Conventional current direction and positive voltage polarity.

Concept / Approach:
Plotting begins at the origin because it represents the neutral reference point of zero excitation and zero response. From there, measurements extend into the first quadrant (forward bias) and third quadrant (reverse bias with negative current according to sign convention) as appropriate for the device under test.

Step-by-Step Explanation:
Set up axes: V on x-axis, I on y-axis.At V = 0, I = 0 → starting point is the graph origin.Increase V forward: observe exponential I rise (first quadrant).Apply reverse V: observe small leakage current (third quadrant) until breakdown.

Verification / Alternative check:
Standard semiconductor texts and datasheets present I–V characteristics referenced to the origin for clarity of bias regions and for easy identification of thresholds such as V_f and breakdown voltage.

Why Other Options Are Wrong:

• “3rd quadrant” alone omits the origin and forward region; the plot encompasses multiple quadrants.
• “Current plot” and “voltage plot” are vague and not positional on the axes.

Common Pitfalls:

• Confusing sign conventions; some plots show reverse current as negative.
• Assuming linear behavior; diode curves are exponential in forward bias.

Final Answer:
graph origin