Differential noise measurements: sensitivities and uncertainties with direct correlation- and balun-based methods

Differential amplifiers and converters are ubiquitous and explicit differential noise measurements of these are of increasing importance. Among the possible techniques are those performing direct correlation of the DUT noise waveforms and those using a characterized balun to make it into one or more single-ended measurements. Both measurement classes have variations that can lead to differences in uncertainties and sensitivities. Several versions will be examined, through measurement and simulation, as a function of DUT configuration (different phasing and levels of correlation) and receiver/balun characteristics (mismatch, imbalance) versus perturbations including calibration errors and external noise ingress. In these experiments, a directly-measured calibration approach and a comprehensive balun model can have similar sensitivities (but with different levels of effort) which can be up to an order of magnitude lower than those for a partially implemented balun model.