ExpEYES

The schematic is wired as shown in the diagram below. The voltage across the diode is measured on A1. The anode of the diode is connected to PV1, through a 1k resistor. Voltage at PV1 is incremented in steps and at each point the voltage across the diode is measured. The current is calculated from i = (PV1-A1)/R. The diode used is 1N4148, silicon diode. The experimental setup and the screenshot are shown below. The results shown are for 1N4148 silicon diode, red and green LEDs.

Python Code

A Python code may be written to plot the IV graph. The applied voltage is incremented in steps and voltage across he diode is measured. The current is (Vapplied - Vdiode)/Resistance.

• Python program to generate VI characteristics and save the data.
• Sample Data
• Python program to analyse the data to extract the Boltzmann constant.

Exracting Boltzmann Constant from V-I data

The V-I data can be fitted with the equation $ I = I_o e^{\frac{qV}{nkT}} $, where

• q - Charge of electron
• k - The Boltzmann constant
• T - Temperature in Kelvin
• n - The ideality factor of the PN juncion. It’s value is ~1 for Germanium, and ~2 for Silicon