Measurement 1/f Noise

Question

Hi, 
 I'm a DFAE in Japan. One customer give me a question about below link. 
 https://www.analog.com/en/analog-dialogue/articles/understanding-and-eliminating-1-f-noise.html 
 According to this article, the 1/f noise is measured with the amplifier gain set to 100. Are all ADI op amp products measured this way? When the gain is 1, is there any change in the 1/f noise characteristics? 
 Regards, 
 Hiroyuki

maaarmas · Accepted Answer

Hi Hiroyuki, 
 It is a different case for instrumentation amplifiers because there's an integrated resistor network which contributes noise as well. Hence, it cannot be directedly divide by the gain. 
 Thanks, 
 Mae)

maaarmas · Answer

HI Hiroyuki.D , 
 We measure the 1/f noise by amplifying the gain, typically it is set to 100, but not always, because we want to amplify the noise in the noise floor as well since the noise is very low that the equipment couldn't measure it. Hence, it depends on the expected noise of the product.

maaarmas · Answer

Hello Hiroyuki, 
 Yes, you will simply divide the noise by the gain when you want to determine the 1/f noise when the gain is 1. 
 Regards, 
 Mae

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Measurement 1/f Noise