Diodes can convert an alternating voltage into a waveform whose load current keeps one polarity.

A half-wave rectifier passes one half-cycle of an AC waveform and blocks the other. A full-wave rectifier, often built as a four-diode bridge, redirects both half-cycles through the load in the same direction.

The rectified waveform still falls between input peaks. Adding a capacitor across the load lets the capacitor charge near a peak and then discharge into the load while the source voltage falls.

The result is a more nearly constant DC output with a remaining periodic variation called ripple. Larger capacitance, lighter load current and shorter time between charging peaks generally reduce the ripple.

Rectifier analysis is piecewise: first determine which diodes conduct, solve the resulting circuit, and then check that the assumed diode states are consistent with the calculated voltages.