SF28 belongs to the high frequency rectifier diode rectifier diode, is referred to as the fast recovery diode, this is because the general rectifier diode is generally work in low frequency (such as mains frequency 50 hz), the working frequency is lower than 3 kHz, when work in a few to several hundred kHz frequency, voltage change direction, time to slow recovery time, ordinary rectifier diode can't normal to achieve single wizard, then with quick restore fast recovery rectifier diode.
SF28 characteristic is its recovery time is short, this feature makes it suitable for high frequency (such as the TV line frequency) in the rectifier.Have a fast recovery diode determines the performance of the important parameters of reverse recovery time.Reverse recovery time is defined as sharp transition to the diode to the from state by state, since output pulse down to zero, to reverse the power back to the maximum 10% of the time required to reverse current, commonly used symbols TRR said.Ordinary fast recovery rectifier diode TRR Andrew bynum for a few seconds (10-9 s), super fast recovery diode TRR general for dozens of nanoseconds.The smaller the Trr fast recovery diode work frequency is higher.