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Noise in in amps

Question asked by dhhsieh on Jun 22, 2017
Latest reply on Jun 26, 2017 by Emman.A

1. The AD8429 has total voltage spectral density noise of 45 nV/rtHz at G=1 and f=1kHz, but the AD797 has less than 1 nV/rtHz at f=1kHz. Is it generally true that in amp packages will have greater noise than op amps? Perhaps because of internal thermal noise from resistors or the extra design considerations for in amps packages.

My application for the in amp is to convert a differential signal to a single-ended signal with respect to ground. See Figure 4 in the attached PDF.

It seems that the minimum (total) voltage spectral density for any gain or frequency for the AD8429 is 45 nV/rtHz.  

 

2. For in amps, as compared with op amps, why are there separate parameters for input voltage noise and output voltage noise? 

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