Digital potentiometer

Another constraint is that special logic is often required to check for zero crossing of an analog AC signal to allow the resistance value to be changed without causing an audible click in the output for audio amplifiers.

Both electro-mechanical and digital potentiometers generally have poor tolerances (typically ±20%),[7] poor temperature coefficients[8] (up to many hundreds of ppm per degree C),[8] and a stop resistance that is typically about 0.5-1% of the full scale resistance.

[7] Digital potentiometer have a limited band width due to parasitic capacitance in device.

[9] Typically a signal span of +15V to -15V is possible, with 16 bit control, i.e. 65535 discrete set points, and drift and non-linearity are negligible.

However a DAC has to be initialised each time the system is powered on, which is typically done by software in an embedded microcontroller.

A multiplying DAC can not be directly used as a rheostat (2 wire connection), but in that mode a digipot performs badly anyway, due to its temperature coefficient and resistance tolerance.