Johnson-Nyquist noise

Let us first shortly consider velocity fluctuation noise. This is the only noise mechanism that exists without electric bias. It is variably denoted as Johnson noise, thermal noise, Nyquist noise, Johnson-Nyquist noise, resistance noise [59, 60]. It is a consequence of stochastic motion of charge carriers within material with finite resistance, and it represents a mechanism to maintain thermal equilibrium in semiconductor [61]. In a general case the spectral density of thermal noise voltage is 5v(co) = 4J (hv/2 + hv/(c " / - l) = 2/flivch(hv/ i,7 ), which in the case hv becomes Sy = Ak TR, i.e., in this case the squared current due to this noise mechanism is... 

In the absence of electrical bias, the absolute minimum internal noise exists, termed Johnson noise, Nyquist noise or thermal noise. This form of noise arises from the random motion of the current carriers within any resistive material and is always associated with a dissipative mechanism. The Johnson noise power is dependent only upon the temperature of the material and the measurement bandwidth, although the noise voltage and current depend upon the value of the resistance. 

Further, we calculate the total noise current as a sum of the squares of generation-recombination noise current obtained in the above manner and Johnson-Nyquist (thermal) current... 

Johnson noise is also known as thermal noise or Nyquist noise. It applies only to resistive elements a feedback resistor, a load resistor, or a PC detector. It does not... 

The proximity of the donor to an oxide interface and nearby electrostatic gates did not introduce additional decoherence. Some coherence measurements are shown in Fig. 5, and the same group have even more recently reported electron Tz times of around 1 ms (with a spin echo) and 0.56 s (with dynamic decoupling), as well as a Tz time for the nucleus with a neutral donor of 1.5 ms for one device and 20 ms for another (both with a spin echo). Ionizing the donor provided a nuclear Tz time of 1.75 s (spin echo) and 35.6 s (with dynamic decoupling). These times are shorter than those measured in bulk Si samples for electrons and nuclei,which was attributed to Johnson-Nyquist thermal noise due to the microwave source. High fidelity control pulses were achieved, reaching 97% for the electron and 99.99% for the nuclear spin. 

A noise that has a clearly distinct origin from noise discussed in previous sections is the electric noise that originates in modulation of ion transport by fluctuations in system conductance. These temporal fluctuations can be measured, at least in principle, even in systems at equilibrium. Such a measurement was conducted by Voss and Clark in continuous metal films (44). The idea of the Voss and Clark experiment was to measure low-frequency fluctuations of the mean-square Johnson noise of the object. In accordance with the Nyquist formula, fluctuations in the system conductance result in fluctuations in the spectral density of its equilibrium noise. Measurement of these fluctuations (that is, measurement of the noise of noise) yields information on conductance fluctuations of the system without the application of any external perturbations. The samples used in these experiments require rather large amplitude conductance fluctuations to be distinguished from Johnson noise fluctuations because of the intrinsic limitation of statistics. Voss and... 

The mean square value of the voltage noise produced by a resistor at the frequency v, with Av band, is known as the Nyquist-Johnson theorem [see also our previous paper ]. 

The minimum value of the noise generated by a system is the thermal or Johnson noise resulting from the random motion of electrons or ions within the system when it is in thermal equilibrium with its surroundings. An expression for the Johnson noise in terms of a fluctuating voltage was first derived by Nyquist [2] in 1928 and takes the form... 

A recent study by DeFelice and Firth (1971) has shown that the electrical noise present in glass microelectrodes is in excess of the Johnson noise predicted by the Nyquist formula given in Section 4.4.3. If the microelectrode lumen is filled with an electrolyte of concentration ri2 and the external electrolyte in which the electrode is immersed has the concentration when = ri2 2i noise voltage is observed as predicted by the Nyquist formula. When Ml offset voltage is noted (tip potential) because of the... 

The Johnson noise of the load resistor R at the temperature T which gives, according to the Nyquist formula, an rms-noise current... 

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