The full wave rectifier is a simple circuit constructed from a combination of four diodes, that helps to convert alternating current (AC) into direct current (DC). The animation below shows the two paths that current can take through the rectifier, depending on which input is the positive voltage. Regardless of the input voltage, the output voltage will always be in the same direction.
Variations in the output voltage can be reduced by adding a capacitor in parallel with the rectifier; the charge / discharge of the capacitor smoothes these variations. Notice that the magnitude of the rectified voltage is always less than the original AC input; this is due to voltage loss across the diodes.