Hi Guys,

Little confusion in Silicon and Schottky.

1N4007 - https://www.vishay.com/docs/88503/1n4001.pdf
SB180 - https://www.diodes.com/assets/Datasheets/ds30116.pdf

The junction capacitance of silicon diode 1N4007 is (Cj) 15pF
The junction capacitance of schottky diode SB180 is (Cj) 80pF
Both diodes did not specified the trr (reverse recovery time ) in datasheet.

why SB180 is called fast switching rectifier diode while 1N4007 is general purpose low frequency diode ?

Guys can you help me to understand which parameter should i look to decide the switching speed of the diode ?

Thanks in Advance !

 

High current and high voltage silicon rectifier diodes like the 1N4007 are used at the very low frequency of 50Hz or 60Hz where fast switching is not needed. They have a fairly high forward voltage which does not matter.

I have used low voltage 1N5817, 1N5818 or 1N5819 Schottky diodes for their low forward voltage. I have never seen a circuit use a SB180 power Schottky diode.

 

why SB180 is called fast switching rectifier diode

Because Schottky diodes have no significant reverse recovery time, unlike silicon junction diodes which do.
General purpose junction rectifier diodes, such as the 1N4007 have a relatively long reverse recovery, while faster signal diodes such as the 1N4148, have a much shorter recovery time, but still longer than a Schottky.

 

why SB180 is called fast switching rectifier diode while 1N4007 is general purpose low frequency diode ?

Guys can you help me to understand which parameter should i look to decide the switching speed of the diode ?

Forward voltage On characteristics. Which is in a plot instead of a flat number entry in a datasheet.
Schottky diodes have a smaller depletion region which has a lower voltage 'ON' characteristics and this lower impedance results in lower thermal noise. That is why they are good with RF designs and rectifiers on the secondary(s) in a switch mode power supply.

Does it mean you always have to use a Schottky diode as a switch mode secondary rectifier? no. But a lot use them in higher current supplies. In other applications in the past, like a CRT TV's flyback secondaries that don't pull a lot of current use a 1N914A as the half wave rectifier.

 

Aside from maximum forward current and average forward current,, and peak revers voltage, diodes have many other specifications that can matter a lot in some applications. Those include switching time, both on and off, which affects the maximum frequency of useful operation, there is also the charge storage capacitance, which controls the switch off time delay when the voltage polarity reverses..

 

Hi Guys,

Little confusion in Silicon and Schottky.

1N4007 - https://www.vishay.com/docs/88503/1n4001.pdf
SB180 - https://www.diodes.com/assets/Datasheets/ds30116.pdf

The junction capacitance of silicon diode 1N4007 is (Cj) 15pF
The junction capacitance of schottky diode SB180 is (Cj) 80pF
Both diodes did not specified the trr (reverse recovery time ) in datasheet.

why SB180 is called fast switching rectifier diode while 1N4007 is general purpose low frequency diode ?

Guys can you help me to understand which parameter should i look to decide the switching speed of the diode ?

Thanks in Advance !

the 1N4007 reverse recovery time (Trr) is specified as 30 us (see the datasheet for test conditions). Being a SBD the SB180 has zero reverse recovery time. Of course in a practical circuit the diodejunction capacitance must be discharged when going from forward to reverse blocking and so there will be reverse current during this time period.

The 1N4007 is suitable for applications having slow dv/dt such as AC power rectification. Not only is it slow to turn off, it is slow to turn on. While forward conduction time is rarely specified I have measured the 1N4007 at around 1 us. That is very slow making it unsuitable for many circuit protection applications such as ESD and as input-to-output diodes in 3-terminal voltage regulator circuits.

General Semiconductor 1N4007 datasheet (this has a Trr spec) https://global.oup.com/us/companion...crocircuits/students/diode/1n4004-general.pdf

Why Schottkey Barrier Diodes have not reverse recovery time?
https://toshiba.semicon-storage.com...-have-reverse-recovery-characteristictrr.html