V-I Curves For Ohmic And Non-Ohmic Devices


To illustrate resistive properties of resistors and diodes.


Oscillator, shunt resistor, test resistor and diode, oscilloscope with scope/TV cart.


Setup Time

10 min.




    A signal generator is used as the source of AC current feeding a series circuit with a shunt resistor and one other "test" circuit component, which can be either a resistor or a diode. The current is displayed on the vertical axis of the oscilloscope as the voltage across a shunt resistor. The voltage across the second element (the element under study) is displayed on the horizontal axis. As seen below, the resistor is a linear or "ohmic" device, but the diode is non-ohmic. The breakdown potential of the diode can be observed.


    Thomas A. Walkiewicz and James R. Kirk, Characteristic Curves, TPT 32, 90-92 (1994).