A fast diode is a faster-than-standard current rectifier. The terms "fast" and "ultrafast" are in comparison to standard rectifiers designed for low-frequency applications such as rectifying sinusoidal current supplied from the AC mains. A “fast” rectifier typically recovers ten times faster than a standard rectifier, and an “ultrafast” designation is usually applied to rectifiers designed to beat the standard rectifier recovery by being more than fifty times faster.

Categorization as "ultrafast", "fast", or "soft" is in reference to the diode's reverse recovery characteristics. "Fast" and "ultrafast" rectifiers are so termed because they cease conducting current in the reverse direction much more quickly than standard rectifiers. "Soft" is a term applied to a subset of ultrafast rectifiers that recover to the non-conducting state quickly, but in a non-abrupt manner.

Diode part numbers
VoltageThrough-hole axial packageSurface-mount package
1 A (DO-41)1.5 A (DO-15)3 A (DO-201AD)6 A (R-6)10 A (R-6)1 A (SMA)2 A (SMB)3 A (SMC)5 A (SMC)
50 VUF4001UF5400US1A
100 VUF4002UF5401US1B
200 VUF4003UF5402US1D
400 VUF4004UF5404US1G
600 VUF4005UF5406US1J
800 VUF4006UF5407US1K
1000 VUF4007UF5408US1M
Datasheet

See also