A bridge rectifier has four diodes arranged in pairs where only one pair conducts current during each half cycle. During the positive half cycle, pair A conducts in series as pair B becomes reverse biased. In negative half cycle, pair A is reverse-biased as pair B conducts in series.
Since current flowing to a load is unidirectional, the voltage across the load also becomes unidirectional with an average across DC voltage of about 0.637 volts. In reality, the current flowing during each cycle goes through two diodes instead of one, so amplitude of output voltage becomes two voltage drops lesser than input voltage amplitude. The ripple frequency now becomes twice the supply frequency.
Although it takes four diodes to build a full-wave bridge rectifier, ready-made bridge rectifier components are available in a range of different current and voltage sizes. These pre-made components are easy to solder directly onto a PCB circuit board or attach using spade connectors.
A typical, pre-made, single-phase bridge rectifier has four connecting leads with one corner cut off indicating that the terminal nearest is the positive output. The cut also indicates that the diagonally opposite lead is the negative. The other leads are for inputting alternating voltage from a transformer?s secondary winding.