Shockley Diode Calculator

Shockley Diode Equation

The Shockley diode equation models the current-voltage relationship of a p-n junction diode. It captures exponential forward conduction and tiny reverse saturation current, forming the basis of semiconductor device modeling.

Equation

$$I = I_s \left(e^{V / (n V_t)} - 1\right)$$

$I_s$ is the reverse saturation current, $V$ is the applied voltage, $n$ is the ideality factor (1 to 2 for real diodes), and $V_t = kT/q \approx 0.026$ V at 300 K.

Forward Bias Example

With $I_s = 10^{-12}$ A, $V = 0.7$ V, $n = 1$, and $V_t = 0.026$ V, the exponent is about 26.9 and forward current reaches hundreds of milliamperes, matching typical silicon diode behavior.

Related tools: Logic Gate Calculator and Op-Amp Gain Calculator.

Frequently Asked Questions

What is the thermal voltage V_t?

Thermal voltage is $kT/q$, about 26 mV at room temperature (300 K). It sets the voltage scale over which diode current rises exponentially.

What does the ideality factor n represent?

The ideality factor accounts for recombination and non-ideal junction behavior. An ideal diode has $n = 1$; real silicon diodes often use $n \approx 1.5$ to 2.

Why subtract 1 in the equation?

At zero bias, $e^0 - 1 = 0$, so net current is zero. The minus one term ensures the equation satisfies equilibrium with no applied voltage.

Does this model reverse breakdown?

No. The Shockley equation describes normal forward and small reverse leakage. Avalanche or Zener breakdown requires additional terms beyond this model.

How does temperature affect diode current?

Both $V_t$ and $I_s$ depend on temperature. As temperature rises, $V_t$ increases and $I_s$ grows, shifting the I-V curve.

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Shockley Diode Equation

Equation

Forward Bias Example

Frequently Asked Questions

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