While half-wave and full-wave rectification suffice to deliver a form of DC output, neither produces constant-voltage DC. In order to produce steady DC from a rectified AC supply, a s
moothing circuit or filter
In its simplest form this can be just a reservoir capacitor
or smoothing capacitor, placed at the DC output of the rectifier. There will still remain an amount of AC ripple
voltage where the voltage is not completely smoothed.
To further reduce this ripple, a capacitor-input filter
can be used. This complements the reservoir capacitor with a choke
(inductor) and a second filter capacitor
, so that a steadier DC output can be obtained across the terminals of the filter capacitor. The choke presents a high impedance
to the ripple current.