BCIT Physics Department

Demonstration Manual

Electricity and Magnetism

DEM55 - Diode (LED) Demonstration


- To illustrate the unidirectional flow of current in diodes, the blocking action of diodes when reverse biased and the polarity and approximate amplitude of waveforms.


DEM55 - Diode (LED) Demonstration


The two LEDs are connected in parallel, "back to front." The "T" is connected to the output of the signal generator, which is set at "X1" Hz, dial at approximately 1.0, amplitude "max."

Coax cables are run to the LED assembly and to the oscilloscope. When the 'scope shows a positive waveform, the red LED will conduct and when it shows a negative waveform the green LED will light.

When showing rectangular or sinusoidal waveforms, the LEDs will be "brightest" at each maximum or minimum. When one LED is on, the other is off due to reverse biasing.