Shockley Diode Equation Calculator — I-V Characteristic
The Shockley ideal-diode equation gives the current through a pn-junction as a function of applied voltage, temperature and material constants. Enter the reverse saturation current, ideality factor and junction temperature to compute the current and plot the full I-V characteristic.
V
°C
Current through the junction at the specified voltage (Shockley equation)
- 1
Temperature in kelvin
25 + 273.15 = 298.15 - 2
Thermal voltage V_T = k_BT/q
k_B × 298.15 / q_e = 25.6926 mVV_T = kT/q ≈ 25.85 mV at 25 °C — sets the sharpness of the exponential turn-on. - 3
Exponent x = V/(n·V_T)
0.6 ÷ (1 × 0.025693) = 23.353 - 4
Diode current I = Is·(eˣ − 1)
0.000000000001 × (e^23.353 − 1) = 0.013871
How does this calculator work?
The Shockley equation I = Is × (e^(V/nV_T) − 1) gives pn-junction current from the saturation current Is, ideality factor n (1–2), and thermal voltage V_T = kT/q (≈ 25.85 mV at 25 °C). Enter any junction voltage to read off the current and see the I-V characteristic curve.
Formula
How this is calculated
The Shockley equation I = Is × (e^(V/nV_T) − 1) models a pn-junction diode. The reverse saturation current Is (typically ~10⁻¹² A for a silicon small-signal diode) sets the overall scale — it is the tiny leakage current under reverse bias. The thermal voltage V_T = kT/q (~25.85 mV at room temperature) converts temperature into a voltage scale: higher temperature → higher V_T → gentler turn-on knee and more reverse leakage.
The ideality (emission) factor n quantifies departure from ideal diffusion-limited transport. n = 1 means ideal; n = 2 indicates recombination in the depletion region dominates. Real silicon small-signal diodes lie between 1.1 and 1.4; Schottky diodes are close to 1; LEDs can reach 2. The I-V curve below plots the characteristic across forward and reverse bias, clipped so the forward knee is visible.
The model has limits: it ignores series resistance (dominates at high forward current), junction breakdown under large reverse bias, high-injection effects, and temperature-dependent Is. For circuit simulation the SPICE diode model extends this with additional parameters.
Frequently asked questions
V_T = kT/q, where k is Boltzmann's constant (1.38 × 10⁻²³ J/K) and q is the electron charge (1.60 × 10⁻¹⁹ C). At 25 °C it equals about 25.85 mV. Because diode current grows as e^(V/nV_T), a 60 mV increase in voltage roughly multiplies the current by 10 (at n = 1, T = 25 °C).
For a common silicon small-signal diode (e.g. 1N4148) Is ≈ 2–10 nA at 25 °C; for power rectifiers it can be microamps; for Schottky diodes 10⁻⁷ A or larger. Datasheets often list reverse current at a specific voltage — you can back-calculate Is from I = Is × (e^(V/nV_T) − 1) with V negative.
At large forward voltage the exponential term e^(V/nV_T) overflows standard double-precision arithmetic (exponents above ~709). In practice, series resistance limits current well before this point; switch to SPICE-level simulation for high-current operating points.
Also known as
TG we-Calculate Editorial Team. (2026). Shockley Diode Equation Calculator — I-V Characteristic [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/shockley-diode-calculator
TG we-Calculate Editorial Team. "Shockley Diode Equation Calculator — I-V Characteristic." TG we-Calculate. 2026. https://we-calculate.com/calculator/shockley-diode-calculator.
TG we-Calculate Editorial Team, "Shockley Diode Equation Calculator — I-V Characteristic," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/shockley-diode-calculator
@misc{wecalculate_shockley_diode_calculator, title = {Shockley Diode Equation Calculator — I-V Characteristic}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/shockley-diode-calculator}}, year = {2026}, note = {TG we-Calculate} }
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