The diode equation describes the exponential current–voltage curve of a p–n junction: almost nothing flows until about 0.6 V for silicon, then current shoots up. Every 60 mV more increases the current roughly tenfold at room temperature.
How to use the Shockley Diode Equation Calculator
- Diode voltage V_D
- Saturation current I_S (A)
- Ideality factor n
- Temperature
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter the diode voltage, saturation current, ideality factor and temperature.
Inputs explained
| Field | What to enter |
|---|---|
| Diode voltage V_D | Units: V, mV, kV, µV, MV |
| Saturation current I_S (A) | A number |
| Ideality factor n | A number |
| Temperature | Units: K, °C, °F |
What each result means
- Thermal voltage V_T = 1.380649e-23×[Temperature]÷1.602176634e-19×1000
- Diode current I = [Saturation current I_S (A)]×(exp([Diode voltage V_D]÷([Ideality factor n]×[Thermal voltage V_T]÷1000)) – 1)
Example values
How the main result changes when Diode voltage V_D changes and everything else stays at the example values above:
| Diode voltage V_D (V) | Diode current I (mA) |
|---|---|
| 0.325 | 2.8824e-6 |
| 0.4875 | 0.0015 |
| 0.65 | 0.8308 |
| 0.8125 | 446.0661 |
| 0.975 | 239,485.4332 |
| 1.3 | 69,030,147,778.7115 |
Formula
I = I_S·(e^{V_D/(n·V_T)} − 1), V_T = k·T/q
Worked example
Inputs — Diode voltage V_D: 0.65 V; Saturation current I_S (A): 1e-14; Ideality factor n: 1; Temperature: 300 K.
Results — Thermal voltage V_T = 25.852 mV; Diode current I = 0.83084 mA.
Key terms
- Saturation current
- Reverse leakage current of an ideal diode.
Frequently asked questions
What is the thermal voltage at room temperature?
About 25.85 mV at 300 K.
What is the ideality factor?
1 for an ideal diode, up to 2 with recombination.
Why is reverse current tiny?
It is limited to the saturation current, about 10⁻¹⁴ A for silicon.
Does the equation work at high current?
Series resistance makes real diodes deviate.