Often the noise figure of a device is specified at a specific temperature (e.g. @ 20 °C) because the noise figure goes up as the temperature goes up in non-linear fashion. The following shows the relationship of noise figure vs. temperature:

For example, what is the noise figure of an amplifier @ 85 °C, having a noise figure of 2.0dB @ 20 °C? Temperatures must be converted to kelvins (K), 20 C = 293K, 85 °C = 358K.

- M. G. (Mar 2000)