Enter Diode Parameters
Example Data Table
| Mode | Diode Type | Input Summary | Expected Behavior |
|---|---|---|---|
| Junction | Silicon | VD = 0.70 V, T = 25 °C, n = 2, IS = 1e-12 A | Moderate forward current with exponential sensitivity. |
| Junction | Germanium | VD = 0.25 V, T = 25 °C, n = 1.3, IS = 1e-6 A | Higher current at lower voltage than silicon. |
| Circuit | Silicon | VS = 5 V, RS = 1000 Ω, T = 25 °C | Solver balances diode law with resistor drop. |
| Circuit | Schottky | VS = 3.3 V, RS = 330 Ω, T = 40 °C | Lower forward drop and stronger conduction. |
Formula Used
The calculator uses the Shockley diode equation:
I = IS × (eVD / (nVT) − 1)
Thermal voltage is calculated from temperature using:
VT = kT / q
Where k is Boltzmann’s constant, T is absolute temperature in kelvin, and q is the electron charge.
In source circuit mode, the page also solves the load-line relation:
VS = VD + I × RS
That nonlinear pair is solved iteratively so the current matches both the diode model and the external resistor.
How to Use This Calculator
- Select either junction voltage mode or source circuit mode.
- Choose a diode preset or keep custom values.
- Enter temperature, ideality factor, saturation current, and diode count.
- For junction mode, enter diode voltage directly.
- For circuit mode, enter source voltage and series resistance.
- Enable manual thermal voltage only when you already know VT.
- Press the calculate button to show the result above the form.
- Use the CSV or PDF buttons to export the computed report.
Frequently Asked Questions
1. What does this calculator estimate?
It estimates diode current, voltage behavior, power, and dynamic resistance using the Shockley equation. In circuit mode, it also includes the effect of a series resistor.
2. Why does temperature matter?
Temperature changes thermal voltage and strongly affects exponential conduction. Higher temperature usually increases current for the same junction voltage in this model.
3. What is the ideality factor?
Ideality factor describes how closely a real diode follows the ideal diffusion model. Typical values are near 1 for Schottky devices and closer to 2 for many silicon junctions.
4. What is saturation current?
Saturation current is the small leakage-related parameter in the Shockley equation. It is usually tiny, but it strongly influences the exponential current curve.
5. Does this model include breakdown?
No. Reverse breakdown, avalanche effects, and Zener behavior are not modeled here. Reverse values represent leakage only unless you supply a separate specialized model.
6. Why use source circuit mode?
Source circuit mode is useful when a diode is connected with a resistor. The solver finds the operating point that satisfies both the diode law and Ohm’s law.
7. What does dynamic resistance mean?
Dynamic resistance is the local small-signal resistance near the operating point. It indicates how much diode voltage changes for a small change in current.
8. Can I use parallel diode count?
Yes. The calculator scales effective saturation current by the number of identical parallel diodes. This is a simplified assumption for matched devices sharing current evenly.