The originator was mystified by the fact that the measured noise was much higher than expected. The mistake in his noise estimate was assuming that the gain of the first stage is 1. While that¡¯s true for the signal path, the noise gain of that stage is about 12. So the voltage noise of the op amp is multiplied by 12, not 1.?
At least that¡¯s what I saw after quickly skimming the article. Mighta missed something along the way¡
Gary NA6O
