This device was commonly used on the output lines of a MicroController. This is frequently approximated with PWM. PWM is perfectly suited to control the sped of motors, or the brightness of LED’s.

It converts a digital binary signal to an output voltage level. With an 8 bit DAC, you could output 256 varying levels of power (including 0 - off).

Most controllers (e.g. the Arduino) do not have DAC outputs, but PWM outputs. An analog result may be obtained by using a capacitor or other intermediate control circuits.