Part 2 of the “Passives aren’t really so passive” series app notes from Maxim Integrated, this time about resistors and their tempco and tolerance degeneration that need to be considered. Link here (PDF)
Passive components don’t draw power but even resistors can, and modify signals in unexpected ways. A resistor’s reaction to temperature, voltage, and signal frequency can often catch the inexperienced engineer by surprise. Tolerances may not be as they seem and simple resistors may provide nonlinear signal response, introducing harmonics where there were none.