Diode Equation Calculator

The Diode Equation Calculator helps calculate the current flowing through a diode by applying the Shockley diode equation. This equation is essential for understanding how diodes behave under different voltages and is widely used in electronics, semiconductor physics, and circuit design.

By using this calculator, engineers, students, and researchers can predict the behavior of a diode in a circuit, ensuring proper component selection and optimizing designs for efficiency and reliability. The calculator applies the diode equation to compute diode current, taking into account factors like temperature, voltage, and material properties.

Formula of Diode Equation Calculator

The diode equation is used to calculate the current flowing through a diode:

Where:

• I (Diode Current) is the current flowing through the diode (in amperes).
• I_s (Saturation Current) is the small leakage current when the diode is reverse-biased. This value is typically very small (in amperes).
• V_d (Diode Voltage) is the applied voltage across the diode (in volts).
• n (Ideality Factor) is a constant that typically ranges between 1 and 2, depending on the type of diode. For silicon diodes, n is typically around 1.
• V_t (Thermal Voltage) is the thermal voltage and is given by the formula:
  V_t = kT / q
  where:
  • k is Boltzmann’s constant (1.38 × 10⁻²³ J/K),
  • T is the temperature in Kelvin (room temperature is typically 300K),
  • q is the charge of an electron (1.602 × 10⁻¹⁹ C).

At room temperature (300K), V_t ≈ 25.85 mV.

This equation allows you to calculate the diode current (I) based on the voltage applied across the diode, its material properties, and temperature.

General Terms for Diode Equation Calculation

Below is a table explaining common terms involved in the diode equation:

Term	Symbol	Definition
Diode Current	I	The current flowing through the diode (in amperes).
Saturation Current	I_s	The small reverse leakage current when the diode is reverse-biased.
Diode Voltage	V_d	The applied voltage across the diode (in volts).
Ideality Factor	n	A constant (typically between 1 and 2) that depends on the diode material.
Thermal Voltage	V_t	The voltage related to temperature, approximately 25.85mV at room temperature (300K).
Boltzmann Constant	k	A constant used in thermal voltage calculation: 1.38 × 10⁻²³ J/K.
Electron Charge	q	The charge of an electron: 1.602 × 10⁻¹⁹ C.

This table serves as a quick reference to understand the terms used in the diode equation.

Example of Diode Equation Calculator

Example 1: Calculating Diode Current at Room Temperature

Let’s calculate the current through a silicon diode with the following properties:

• Saturation Current (I_s) = 10⁻¹² A
• Diode Voltage (V_d) = 0.7 V
• Ideality Factor (n) = 1
• Temperature (T) = 300 K

At room temperature, V_t ≈ 25.85 mV.

Using the diode equation:

I = I_s × (e^(V_d / (n × V_t)) - 1)

Substitute the values:

I = 10⁻¹² × (e^(0.7 / (1 × 25.85 × 10⁻³)) - 1)
I ≈ 10⁻¹² × (5.65 × 10¹¹ - 1) ≈ 0.565 A

Therefore, the current through the diode is approximately 0.565 A.

Example 2: Diode Current for LED Diode

For an LED diode with the following properties:

• Saturation Current (I_s) = 10⁻¹⁵ A
• Diode Voltage (V_d) = 2.0 V
• Ideality Factor (n) = 1.2
• Temperature (T) = 300 K

The calculation would proceed in the same way. First, calculate V_t:

V_t ≈ 25.85 mV.

Now, calculate the diode current using the diode equation:

I = 10⁻¹⁵ × (e^(2.0 / (1.2 × 25.85 × 10⁻³)) - 1)
I ≈ 10⁻¹⁵ × (1.02 × 10⁸ - 1) ≈ 0.102 A

The current through the LED diode is approximately 0.102 A.

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