Ideal Diode Current and Voltage Calculator

This calculator solves for any single missing value in the ideal diode I-V equation for a forward-biased PN-junction diode. Parameters are current, saturation current, voltage, temperature, and ideality factor.

Input Any 4 of the 5 Diode I-V Equation Parameters
Current (ID):
Saturation Current (IS):
Voltage (VD):
Ideality Factor (n):
Temperature (T):

Using the Ideal Diode Calculator

To use this ideal diode equation calculator, enter any four of the five variables and select the desired units. Then, push the Calculate button. The calculator will solve for the missing parameter. The five variables in the ideal diode formula are:

  • Diode current (ID
  • Saturation current (IS)
  • Forward-bias voltage (VD)
  • Ideality (correction) factor (n)
  • Temperature (T)


Basics Operation of a Forward-Biased PN Junction Diode

A PN diode primarily allows current to flow in one direction. When the diode is forward-biased, as illustrated in Figure 1, the current increases exponentially.


Exponential I-V curve of a forward-biased PN junction diode

Figure 1. Exponential I-V curve of a forward-biased PN junction diode


Ideal Diode Current Equation

The forward-biased diode current equation used in this calculator is:

$$$ I_D = I_S \cdot \left( e^{(\frac{qV_D}{nkT})}-1 \right) $$



ID = Diode current in amps (A)

IS = Saturation current in amps (A)

VD = Forward voltage across the diode in volts (V)

e = Euler’s constant = 2.71828

q = charge of an electron = 1.6E-19 in coulombs (C)

n = Ideality diode correction factor

k = Boltzmann’s constant = 1.38E-23

T = Junction temperature in kelvin (K)


The ideality factor, n, is 1 for ideal diodes and, typically, a value between 1 and 2 for non-ideal diodes. 


To learn more about the P-N junction diode, please check out these other All About Circuits resources: