Formula used
The Shockley equation models ideal diode behavior. Series resistance improves high-current voltage estimates. Real breakdown needs a separate physical device model.
How to use this calculator
- Select the calculation mode matching your unknown value.
- Choose a material preset or enter custom properties.
- Enter current, voltage, temperature, and saturation current.
- Add doping, permittivity, bias, and junction-area values.
- Enable comparison, resistance, or custom sweep options.
- Press calculate and review results, warnings, and graphs.
- Copy results or export them as CSV or PDF.
Use consistent physical inputs for meaningful results. Material presets provide practical starting values. Manufacturer data remains essential for final engineering decisions.
Example data
| Example | Material | Current or voltage | Temperature | Main purpose |
|---|---|---|---|---|
| Silicon at 1 mA | Silicon | 1 mA | 25 °C | Forward voltage |
| Silicon at 10 mA | Silicon | 10 mA | 25 °C | Series loss comparison |
| Germanium junction | Germanium | 1 mA | 25 °C | Lower voltage material |
| High-temperature diode | Silicon | 1 mA | 125 °C | Temperature influence |
| Reverse leakage | Silicon | −5 V | 25 °C | Reverse current estimate |
| Built-in potential | Silicon | 10¹⁶ cm⁻³ doping | 25 °C | Barrier voltage |
| Depletion analysis | Silicon | 5 V reverse bias | 25 °C | Width and field |
Frequently asked questions
What is PN junction voltage?
It is the voltage across a semiconductor junction. Its value depends on current and temperature. Material properties also affect the measured operating voltage.
What is the built-in potential?
It is the equilibrium barrier inside the junction. Doping and intrinsic concentration determine its magnitude. No external current is required for its existence.
How is diode forward voltage calculated?
The calculator rearranges the Shockley diode equation. It uses current, saturation current, temperature, and ideality. Series resistance can increase the terminal voltage.
What is reverse saturation current?
It is a small model current parameter. It strongly affects calculated forward junction voltage. Temperature changes its real value substantially.
What does the ideality factor mean?
It adjusts the diode equation for recombination behavior. Ideal diffusion often approaches a value near one. Practical junctions commonly use values between one and two.
How does temperature affect junction voltage?
Thermal voltage rises as absolute temperature increases. Real saturation current also increases strongly. Device voltage usually falls at constant forward current.
Why is silicon voltage often near 0.7 volts?
That value is a common practical approximation. Actual voltage changes with current and device construction. Temperature and resistance also shift it.
What is thermal voltage?
Thermal voltage equals Boltzmann's constant times temperature, divided by charge. It is about 25.7 millivolts near room temperature. Diode equations scale voltage using this quantity.
What is depletion width?
It is the carrier-depleted region around the junction. Reverse bias usually makes this region wider. Doping and permittivity control the calculated width.
Does the Shockley equation include breakdown?
No, ordinary Shockley modeling excludes avalanche breakdown. Large reverse voltages therefore need another model. Heed the warning shown by this calculator.
Why can measured voltage differ from calculation?
Real devices include resistance, self-heating, and leakage. Parameters also vary between manufacturing batches. Use datasheets for final circuit design verification.
Engineering note
This calculator provides educational and preliminary engineering estimates. It does not replace verified semiconductor models. Confirm critical designs using manufacturer specifications and laboratory measurements.