The 1N400x (or 1N4001 or 1N4000^[2]) series is a family of popular 1 A general-purpose silicon rectifier diodes commonly used in AC adapters for common household appliances. Its blocking voltage varies from 50 volts (1N4001) to 1000 volts (1N4007). This JEDEC device number series is available in the DO-41 axial package,^[3][4] and similar diodes are available in SMA and MELF surface mount packages (in other part number series).^[5][6]

The 1N540x (or 1N5400) series is a similarly popular family of diodes for higher-current 3 A applications. These diodes are typically available in the larger DO-201AD axial package to dissipate heat better.^[7][8]