Noise generator
A noise generator is a circuit that produces electrical noise (i.e., a random signal). Noise generators are used to test signals for measuring noise figure, frequency response, and other parameters. Noise generators are also used for generating random numbers.[1]
Theory[edit]
There are several circuits used for noise generation. For example, temperature-controlled resistors, temperature-limited vacuum diodes, zener diodes, and gas discharge tubes.[2] A source that can be switched on and off ("gated") is beneficial for some test methods.
Noise generators usually rely on a fundamental noise process such as thermal noise or shot noise.
Thermal noise generator[edit]
Thermal noise can be a fundamental standard. A resistor at a certain temperature has a thermal noise associated with it. A noise generator might have two resistors at different temperatures and switch between the two resistors. The resulting output power is low. (For a 1 kΩ resistor at room temperature and a 10 kHz bandwidth, the RMS noise voltage is 400 nV.[3])