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Incoming links: John Bertrand Johnson
By John Bertrand Johnson, published as J. B. Johnson. Physical Review 32, 97–109; published 1 July 1928.
Thermal electrical noise 2026-10-18
Thermal electrical noise is the fluctuating electric potential difference or electric current produced by thermal fluctuations in a dissipative electrical circuit, even without an applied voltage. A resistor at thermal equilibrium is both a source of noise and a sink for electrical energy. Its electrical resistance describes the dissipation, and its absolute temperature sets the scale of the fluctuations. This connects a practical limit on signal-to-noise ratio to statistical mechanics: a warm, unbiased resistor is not electrically silent.
John Bertrand Johnson measured the effect using a vacuum-tube amplifier and thermocouple; his 1928 paper reported agreement with the Boltzmann constant. Harry Nyquist's companion paper calculated the effect from thermodynamics and statistical mechanics.[ref]
Thermal Agitation of Electricity in Conductors by John Bertrand Johnson. Johnson, Thermal Agitation of Electricity in Conductors, Physical Review 32, 97–109 (1928), abstract: amplifier and thermocouple measurement
[ref]Thermal Agitation of Electric Charge in Conductors by Harry Nyquist. Nyquist, Thermal Agitation of Electric Charge in Conductors, Physical Review 32, 110–113 (1928), abstract: thermodynamic and statistical calculation