White noise is a random signal (or process) with a flat power spectral density. In other words, the signal contains equal power within a fixed bandwidth at any center frequency. To measure and test a wide band communication circuit we can use this noise. But to build the generators we need more money. This article shows the cheaper way to build white nose generators.

low cost noise generator circuit schematic

The generator shown in this article uses a zener breakdown phenomenon, which generate the avalanche noise. when a PN junction is operated in the reverse breakdown mode, the zener breakdown is created. The avalanche noise has much more intense and has a flat frequency spectrum (white) than shot noise but both  are very similar. Since it’s depends on the materials, the magnitude of the noise is difficult to predict.

Essentially the circuit has 2 portions: MAX2650 Low Noise Amplifiers (LNA) and a zener diode.The MAX2650 is a wide-band Low-Noise-Amplifier with 19dB gain operating from DC to 1GHz. We use the diode is reverse-biased and noise output is taken from the anode.