Photodiode Current Equation — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Photodiode Current Equation This equation describes the net current-voltage (I-V) characteristic of a photodiode when it is illuminated by light and biased by an external voltage. Start with the standard Shockley diode equation for the diode current (I diode). Recognize that the incident light generates a photocurrent (I L) proportional to the light intensity. The total current (I) is the difference between the diode current and the photocurrent: I = I diode - I L. Substitute the exponential diode term into the net current equation. The ideality factor n is typically between 1 and 2. V T (Thermal Voltage) is approximately 25.8 mV at room temperature. The applied voltage V must be non-zero for the exponential term to be meaningful. Confusing the total current (I) with just the diode current (I diode). Forgetting that the photocurrent (I L) acts to reduce the net current. Assuming the current-voltage relationship is linear, especially at low voltages.