A complete operational amplifier noise model: Analysis and measurement of correlation coefficient

In contrast to the general operational amplifier (op amp) noise model widel y used, we propose a more complete and applicable noise model, which consid ers the correlation between equivalent input voltage noise source e(n) and current noise source i(n). Based on the super-position theorem and equivale nt circuit noise theory, our formulae for the equivalent input noise spectr um density of an op amp noise are applied to both the inverting and noninve rting input terminals. By measurement, we demonstrate that the new expressi ons are significantly more accurate. In addition, details of the measuremen t method for our noise model parameters are given. A commercial operational amplifier (Burr-Brown OPA37A) is measured by means of a low-frequency nois e power spectrum measuring system and the measured results of its noise mod el parameters, including the spectral correlation coefficient (SCC), are fi nally given.