Thermal Characteristic
An analog electrical response decreases linearly in magnitude as the operating temperature rises. This complementary to absolute temperature characteristic typically appears in the forward voltage of a silicon p-n junction.
Circuit Implementation
A constant current source biasing a bipolar junction transistor produces the desired voltage drop across the base-emitter terminals. The resulting signals are used to generate stable reference voltages when combined with proportional counterparts. Designers adjust the current density to fine-tune the temperature coefficient to exactly match the required slope.
Drift Influence
Longitudinal mechanical stress on the packaging material causes subtle deviations in the linear output over extended operating periods. If the silicon die bends under package pressure, the complementary to absolute temperature sensor exhibits a minor offset in its base voltage. Regular system calibrations help mitigate this drift to maintain high measurement accuracy.
Compensation Mechanism
A bandgap reference combines negative and positive thermal coefficients to create a stable voltage that remains constant across a wide temperature range. By summing the complementary to absolute temperature voltage with a proportional to absolute temperature signal, the overall variation is reduced to near zero. This cancellation relies on precise ratio matching of internal resistors to achieve the required balancing across hundreds of degrees.
