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Ultrafast recovery diodes

Currently designing something for which an ultrafast recovery diode is recommended but on checking the specs and package types for devices so classified at Digikey, I don't like what I see....Current ratings start at

1A which is much more than I need and SMD package types are typically large and bulky SMB or SMA. Forward and reverse recovery times are typically 25 - 50ns.

Looking at some switching diodes not claiming to be fast, superfast or ultrafast, I see current ratings and package types right up my street. Reverse recovery times are as low as 4ns but no mention is made of forward recovery times. Two questions...What are all the relevant attributes of a ultrafast recovery diode? Why wouldn't a switching diode with a 4ns reverse recovery time not be more than suitable as an ultrafast recovery diode?

Reply to
oparr
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4ns sounds like a schottky diode or small-signal diode. These are all fast and don't have to be explicitly hyped as "ultrafast".

AFAIK there are no special required attributes or values for "ultrafast", "fast", "standard" etc. It depends on the manufacturer or reseller and is mostly marketing talk. E.g. the BYW98 (50ns trr) diode is called "fast recovery" by ST, but all resellers seem to think it's "ultrafast".

Diodes may also be named "slower" than what they are. For example the 1n4148 (max 4ns trr) is usually either called "small-signal" or "fast", but haven't seen "ultrafast" anywhere yet.

And then there's also "soft recovery", but again, what can be considered an objective criteria to qualify as "soft recovery"? :-)

So, summary: marketing BS. But okay, I'm not in the semiconductor&process business, so maybe someone else can give a better answer or correct me here...

- Jan

Reply to
Jan Wagner

Apparently you've never googled for one yet then. They are used in SPSs when Schottkys don't have enough reverse breakdown. They're like ordinary silicon diodes, but not with the Schottky doping but with doping and other characteristics that minimize reverse carrier recovery time, making them "ultrafast", like, switching in times comparable to a Schottky or signal diode, but at power diode power levels.

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Cheers! Rich

Reply to
Rich Grise

Don't forget ultrafast's brother, or sister, ultrasoft.

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--
 Thanks,
    - Win
Reply to
Winfield Hill

These would make a nice, wide range varactor. 470 pF to 47 pF with less than a 10 volt bias change.

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Reply to
John Popelish

Google? What's that?

Yes, that's about right. Trr is specified at higher current levels (typically 500ma as >

Reply to
oparr

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