After my previous blogs on noise, I got an email from PJ, a very knowledgeable reader, calling attention to my casual intermingling of the terms “current noise” and “noise current.” He makes a clear distinction between the two and would reserve the term “current noise” for excess resistor noise caused by the flow of a DC current. I have not written on this source of noise and do not consider myself particularly knowledgeable on the topic.
Here is what PJ wrote:
"D.C. current through resistors results in a noise voltage which is a form of excess noise with a spectral density that falls with increasing frequency (1/f). Because the magnitude of this particular noise voltage is proportional to the DC current flowing, it is termed ‘current noise’ and typically modeled (Thevenin-wise) as a noise voltage source.
This can seem a bit pedantic, and I only became sensitive to the very subtle difference when I was a bit loose with it myself, and some EE students became confused about it. Practicing engineers often have tolerance to these things, and this one would crop up only rarely (if ever), but such ambiguities can be unnecessarily frustrating to those new to and unfamiliar with noise analysis/design--which is already complicated enough. Bruce is to be commended for making this area accessible.”
While I understand PJ’s point, I confess ignorance. My ear hears little difference between the two and I would rely on context make the distinction.
What say you? Before reading this, did you make a distinction? After reading, do you think we should make a distinction? Would there be better or clearer terminology?
Thanks and please comment below. -- Bruce
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