Page "Diode" Paragraph 123

A diode can be used as a temperature measuring device, since the forward voltage drop across the diode depends on temperature, as in a silicon bandgap temperature sensor.

From the Shockley ideal diode equation given above, it might appear that the voltage has a positive temperature coefficient ( at a constant current ), but usually the variation of the reverse saturation current term is more significant than the variation in the thermal voltage term.

Most diodes therefore have a negative temperature coefficient, typically − 2 mV /˚ C for silicon diodes at room temperature.

This is approximately linear for temperatures above about 20 kelvins.

Some graphs are given for: 1N400x series, and CY7 cryogenic temperature sensor.