Resistor Model
Integrated resistors are not ideal, but exhibit a voltage and temperature dependence.
An integrated Pinched Resistor employs a high-resistance well bounded by two inversely doped regions. These reversed diodes will “pinch” the conductive region depending on the voltage between them.
A typical example is the Nwell-resistor:
A quadratic temperature dependence is an appropriate model for most resistors.
It is modeled around a central (or nominal) temperature T0,
which is part of the specification.
Below is the measured temperature dependence of a 100 kΩ Poly2-resistor.