Diode I-V Characteristic Curve

1️⃣ Diode I-V Characteristic Curve

The diode characteristic curve (I–V curve) shows how the current (I) through a diode changes with the voltage (V) across it.

• Forward Bias (Positive voltage across diode):
• Current is almost zero until the diode reaches around 0.6–0.7 V (for silicon diodes).
• Then current increases exponentially with voltage.
• Reverse Bias (Negative voltage across diode):
• Current is very small (leakage current).
• When the voltage reaches the breakdown voltage, current increases sharply (for Zener or avalanche diodes).

2️⃣ Measuring Diode I-V Curve with an oscilloscope

X-Y Mode Method with series Resistor

VAC small AC Voltage source

R: Series resistor to limit current

X: input voltage across the diode

Y: input voltage across the resistor

Oscilloscope setting:

set to X-Y mode

Connect X ➡️ diode voltage, Y ➡️ resistor voltage

✅ Application of the Diode I-V Curve

1. Check diode type and condition

2. Measure diode forward voltage

3. Analyze rectifier and switching circuits

4. Measure breakdown voltage for Zener diodes