In very simple cases, it is more cost effective to use an analog filter.

In an analog filter, the input signal is "directly" manipulated by the circuit.

Even if the design could be achieved using analog filters, the engineering cost of designing an equivalent digital filter would likely be much lower.

While these techniques are possible in an analog filter, they are again considerably more difficult.

Digital filters also tend to be more limited in bandwidth than analog filters.

The design of linear analog filters is for the most part covered in the linear filter section.

A stable current or voltage is switched into a low-pass analog filter with a duration determined by the digital input code.

The capacitors (or inductors) in the analog filter have a "memory" and their internal state never completely relaxes following an impulse.

Oversampling can make it easier to realize analog anti-aliasing filters.

In modern integrated circuit technology, digital filters are easier to implement than comparable analog filters.