Questions tagged [johnsonnyquist]

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Trouble to understand Johnson Nyquist noise: why I don't find the “4” in the voltage fluctuation

I am a little bit confused to precisely understand the meaning of the formula: \$\langle \overline{V}^2 \rangle=4 k_b T R \Delta f\$ Imagine a resistor \$R\$ in \$x=0\$ thermalized at temperature \$T ...
2
votes
1answer
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How to measure Johnson Noise precisely experimentally?

I want measure Johnson Noise across a resistor having certain over the certain range of frequency or bandwidth practically. I am starting from scratch, how can I build circuitry and instrumentation so ...
3
votes
2answers
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Johnson–Nyquist Noise of Open Circuit

Johnson–Nyquist Noise increases with resistance - so does it become infinite for an open circuit? Specifically why is the input to an oscilloscope that is not connected to anything not completely ...