electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

, electrothermal feedback is the interaction of the electric current and the

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

in a device with a temperature-dependent

electrical resistance The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual paralle ...

. This interaction arises from Joule heating. The temperature-dependence of the electrical resistance is described by the

derivative In mathematics, the derivative of a function of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. ...

of the resistance with respect to temperature ''dR/dT''. Semiconductors typically exhibit a negative ''dR/dT''.

Superconductors Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike ...

exhibit a large positive ''dR/dT'' on the superconducting phase transition. Normal (non-superconducting)

metals A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typical ...

typically exhibit a positive ''dR/dT'' that decreases to zero at very low temperatures. If a device has a positive ''dR/dT'', an increase in temperature (for example, due to

thermal fluctuations In statistical mechanics, thermal fluctuations are random deviations of a system from its average state, that occur in a system at equilibrium.In statistical mechanics they are often simply referred to as fluctuations. All thermal fluctuations b ...

or the absorption of a

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they a ...

) will increase the electrical resistance ''R''. If the device is biased with a constant voltage ''V'', this increase in resistance will decrease the Joule power ''P = V²/R''. The decrease in Joule heating will cause the device to return to its equilibrium temperature. This is known as negative electrothermal feedback, as the change in Joule heating opposes the change in temperature. If the device is instead biased with a constant current ''I'', the Joule power ''P = I²R'' will increase if the temperature increases. Thus the Joule heating amplifies a change in temperature, an effect known as positive electrothermal feedback. The situation is reversed for the case of a negative ''dR/dT''. Electrothermal feedback is important for describing the performance of several types of photodetectors such as the

bolometer A bolometer is a device for measuring radiant heat by means of a material having a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley. Principle of operation A bolometer ...

, the transition edge sensor,K.D. Irwin, "An application of electrothermal feedback for high resolution cryogenic particle detection," ''Appl. Phys. Lett.'' 66, 1998 (1995), and the superconducting nanowire single-photon detector.

References

{{reflist Superconducting detectors