Aim

To plot the VI characteristics of a pn junction diode.

Components

Theory

The circuit diagram to plot the VI characteristics of a pn junction diode is shown. Applying a positive potential to the anode and a negative potential to the cathode of the pn junction diode establishes a forward bias condition on the diode. As the applied potential is increased the depletion region width decrease and conduction of electron increase. In general the characteristics of the semiconductor diode can be defined by the equation

Where I_S = reverse saturation current

k=11600/h with h =1 for Ge and 2 for Si.

T_K=T_C+273

T_K = Temperature in ° Kelvin

T_C = Temperature in ° Centigrade

V_D = Applied potential

I_D = Diode current

For positive values of V_D, I_D is positive and increases exponentially. At V_D=0, I_D is also zero (ref: equation). For negative values of V_D, I_d = -I_s which is a horizontal line. This explains the VI characteristics of pn junction diode.

Procedure

EDWinXP Project Explorer -> Page(MAINPAGE) -> Edit Page: The circuit diagram is drawn in the schematic editor page by loading components from the library. Wiring and proper net assignment has been made. The resistor R is assigned a proper value.

EDWinXP ->Preferences -> Mixed Mode Simulator: The circuit is preprocessed. The VI characteristics may be obtained by performing DC Sweep Analysis. The current waveform marker is placed at the anode of the diode. The sweep parameter (voltage) for input source is set in the Analysis window. The applied voltage is swept from an initial value of 0 to final value of 1V in steps of 1mV. To get VI characteristics, the currents corresponding to varying input voltages are noted. The VI graph is observed in the Waveform Viewer.

Result

The output waveform may be observed in the waveform viewer