Multi-channel cross-correlation for increasing sensitivity in voltage noise measurements

In this paper we demonstrate that if N (N>;2) voltage amplifiers are connected to the device under test when performing voltage noise measurements in a situation in which the equivalent voltage noise of each single amplifier is larger than that to be measured, the time required for obtaining a given accuracy is reduced by a factor N(N-1)/2 with respect to the conventional set-up employing just two amplifiers. Measurements on two different set-ups employing up to 4 channels and up to 8 channels are presented that confirm that the expected reduction factors in measurement time by a factor of 6 and 28, respectively, are indeed obtained in actual experiments.