Avalanche noise


"Avalanche noise in semiconductor devices is associated with reverse-biased junctions. For large reverse junction voltages the leakage current can be multiplied by the avalanche phenomenon. Carriers in the junctions gain energies in a high electrical field and then they collide with the crystal lattice. If the energy gained between collisions is large enough, then during collision another pair of carriers (electron and hole) can be generated. This way the revised biased current can be multiplied. This is a random process and obviously the noise source is associated with the avalanche carrier generation.  The intensity of the avalanche noise is usually much larger than any other noise component. The avalanche phenomena is often used to build noise sources"  - source

The basic avalanche noise circuit I used in the testing on this page was first posted to sci.crypt Usenet newsgroup in the late nineties.  It basically uses a reverse biased NPN transistor as a reverse biased diode as the noise source and a second transistor as an amplifier for this noise.  The basic circuit is as follows, along with a oscilloscope screen capture that shows the noise output of the circuit at 12V DC


Typical noise output waveform from the above circuit


The current information on my testing of this circuit along with test data can be found here: Google Code page

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