Diode Law

The diode law, often referred to as the Shockley diode equation, describes the current-voltage (I-V) characteristic of a diode. This law is fundamental in understanding the behavior of semiconductor diodes.

Shockley Diode Equation

The Shockley diode equation or current diode equation is given by:

Where:

• I is the diode current.
• I0​ is the reverse saturation current (a very small current that flows through the diode when it is reverse-biased).
• V is the voltage across the diode.
• q is the charge of an electron (approximately 1.602×10^−19 coulombs).
• k is the Boltzmann constant (approximately 1.381×10^−23 joules per kelvin).
• T is the absolute temperature in Kelvin.

Image Source: Diode Current Equation-Electricalvolt

Key Aspects of the Diode Law

1. Forward Bias: When a positive voltage is applied to the p-side of the diode (forward bias), the exponential term e^qV/KT becomes much larger than 1, and the current I increases rapidly with increasing V.
2. Reverse Bias: When a negative voltage is applied to the p-side of the diode (reverse bias), the exponential term e^qV/KT is very small, and the current I is approximately equal to −I0​, which is the small reverse saturation current.
3. Temperature Dependence: The diode current is strongly dependent on temperature. As the temperature increases, the thermal voltage (KT/q​) increases, leading to a larger forward current for a given forward voltage.
4. Saturation Current: I0​ is a key parameter that depends on the material properties of the diode and the temperature. It typically increases with temperature because more minority carriers are thermally generated.

Reference: Current Equation of a Diode- Electricalvolt.com