The
silicon bandgap temperature sensor is an extremely common form of temperature sensor (
thermometer) used in electronic equipment. Its main advantage is that it can be included in a silicon
integrated circuit at very low cost. The principle of the sensor is that the forward voltage of a
silicon diode is temperature-dependent, according to the following equation:
- <math>V_{BE}=V_{G0}(1-{T/T_0})+V_{BE0}(T/T_0)+(nKT/q)\ln(T_0/T)+(KT/q)\ln(IC/IC_0)</math>
where
- T = temperature in kelvin
- V_{G0} = bandgap voltage at absolute zero
- V_{BE0} = bandgap voltage at temperature T_{0} and current IC_{0}
- K = Boltzmann's constant
- q = charge on an electron
- n = a device-dependent constant
By comparing the bandgap voltages at two different currents, IC
_{1} and IC
_{2}, many of the variables in the above equation can be eliminated, resulting in the relationship:
- <math>\Delta V_{BE}=(KT/q)\ln(IC_1/IC_2)</math>
An electronic circuit, such as the
Brokaw bandgap reference[?], that measures ΔV
_{BE} can therefore be used to calculate the temperature of the diode. The result remains valid up to about 200°C to 250°C, when leakage currents become large enough to corrupt the measurement. Above these temperatures, more exotic materials such as
silicon carbide can be used instead of silicon.
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