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 Voltage Through-hole axial package Surface-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 V UF4001 UF5400 US1A 100 V UF4002 UF5401 US1B 200 V UF4003 UF5402 US1D 400 V UF4004 UF5404 US1G 600 V UF4005 UF5406 US1J 800 V UF4006 UF5407 US1K 1000 V UF4007 UF5408 US1M Datasheet
See also Diode 1N400x general-purpose diodes
References