if thermal noise exists while no currents in resistor

alvays said:

Will the thermal noise still exists or not?

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timof said:

alvays said:

Will the thermal noise still exists or not?

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Yes, thermal noise is present irrespective of the current in or voltage on the resistor.
The thermal noise (power spectral density - i.e. power per Hz of frequency bandwidth) is given by: S=4kTR, so there is no current of voltage entering this formula.

Some other noise mechanisms do depend on current, for example - generation-recombination noise, shot noise, etc.

A more interesting question is - does thermal noise affect the voltage noise on a capacitor?

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alvays said:

timof said:

A more interesting question is - does thermal noise affect the voltage noise on a capacitor?

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thanks.

I think the answer is yes if there is a resister in parallel with the capacitor. Though the integrated noise over the all bandwidth is determined by kT/C, but the instantaneous one, that is, the random noise should be there any time.

alvays

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