A bridge rectifier is a device made up of four diodes, used to convert an alternating current (AC) input into direct current (DC) output. By using four diodes in a closed loop configuration, the bridge rectifier is able to convert both the positive and negative voltage peaks of the AC sine wave into positive voltage DC output. A bridge rectifier is necessary in some applications, such as powering a motor from a single phase AC source, because the motor can only use a DC power input. Additionally, for many applications, the output of a bridge rectifier is then passed through a filter capacitor to smooth out any residual ripple in the output voltage.