Avalanche noise 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. Fortunately, the avalanche noise exists only in the pn junction biased with a voltage close to the breakdown voltage. The avalanche phenomenon is often used to build the noise sources.