explain the Diode Characteristics and Temperature Dependence of Barrier Potential An ordinary resistor is a linear device because the current vs voltage graph is a straight line. A diode is nonlinear device, meaning the current vs voltage graph is not a straight line. The reason is the barrier potential or cut-in voltage. When the diode voltage is less than the barrier potential, the diode current is small. When the diode voltage exceeds the barrier potential, the diode current increases rapidly. In this experiment you will measure diode currents and voltages for both forward and reverse bias configuration. This will allow you to draw diode curve. Further you will study the temperature dependence on the cut-in voltage (or barrier potential) of the diode. Band Theory: When an atom is isolated, the orbit of an electron is influenced only by the charges of the isolated atom. This results in energy levels like the lines as we know. However when the same atom is placed in a crystal, the orbit of each electron is influenced by the charge of many other atoms. Since each atom has a unique position inside the crystal, no two electrons see exactly the same pattern of surrounding charges