White Noise Generators 

White noise generator circuits using Zener diodes or base-emitter junctions in avalanche are very simple to build, and can be used in a variety of applications, such as electronic music, sound effects, and test equipment.

Zener diode white noise generator circuits

Zener diodes are PN junction diodes that are designed to operate in reverse breakdown. When a Zener diode is reverse biased, a high electric field is created across the junction, which causes electrons to tunnel through the barrier. This tunneling process is a random event, and it produces a wideband noise signal.

To build a simple white noise generator circuit using a Zener diode, simply connect the diode in series with a resistor to a power supply. The value of the resistor should be chosen such that the current through the diode is within the recommended operating range. The output of the circuit can be taken from either side of the resistor.

Base-emitter junction white noise generator circuits

The base-emitter junction of a transistor can also be used to generate white noise. When the base-emitter junction is reverse biased (5 to 12 V), it also breaks down in avalanche, and this produces a random noise signal.

To build a white noise generator circuit using a base-emitter junction, simply connect the base and emitter terminals of the transistor to a power supply, with a resistor in series to limit the current. The output of the circuit can be taken from the collector terminal of the transistor.

Zener diode white noise generator.

Base emitter white noise generator.

Class C white noise generator.