About Reverse Saturation Current
Reverse saturation current is a small diode current. It is the current scale in the Shockley diode equation. It strongly affects forward voltage, leakage estimates, and circuit bias. Designers often call it Is, I0, or saturation current.
Why It Matters
A tiny change in Is can move a diode curve. It changes predicted current at a fixed voltage. It also helps compare silicon, Schottky, and germanium devices. Low Is usually means lower leakage. Higher Is often appears with larger junction area or warmer temperature. The value is not fixed forever. It rises with temperature and process spread.
Measurement Inputs
This calculator extracts Is from a measured diode current and voltage. It uses temperature to calculate thermal voltage. It also accepts an ideality factor. That factor describes how close the diode is to an ideal junction. A value near one fits diffusion current. A value near two often fits recombination current. Real diodes can sit between those values.
Series Resistance
Series resistance can hide the true junction voltage. At higher currents, some applied voltage drops across leads and bulk material. The calculator subtracts I times Rs from the applied voltage. That corrected value is the junction voltage used in the equation. Use zero resistance when the effect is unknown. Use measured resistance when you have test data.
Area Normalization
The area field gives current density. This helps compare devices of different sizes. A larger diode can show a larger Is, even with the same material quality. Current density removes much of that size effect. It is useful in wafer tests and device modeling.
Practical Tips
Use steady temperature during measurement. Avoid self heating at high current. Select a voltage where the diode curve is exponential. Very low voltage can make noise important. Very high current can make resistance dominate. Repeat measurements at several points when accuracy matters. Export the result for lab notes, reports, or simulation records.
Using the Result
The calculated value is a model parameter, not a guaranteed limit. Datasheets may list leakage under different voltage and temperature conditions. Compare values only after checking those conditions. For simulation, enter Is with the same ideality factor used here. Then tune resistance, capacitance, and temperature separately, carefully.