Ideal Diode Current and Voltage Calculator

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 (I_D) 
• Saturation current (I_S)
• Forward-bias voltage (V_D)
• 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.

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:

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

where:

I_D = Diode current in amps (A)

I_S = Saturation current in amps (A)

V_D = 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:

• The Exponential Current–Voltage Relationship in Forward-Conducting Diodes (technical article)
• The PN Junction Diode and Diode Characteristics (video tutorial)