If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #1667
Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374
forward recovery defines an inductive behaviour at turn-on. It is being attributed to parasitic inductivity but perhaps electron mobility limitations play a role here, too.
Registered Member #2941
Joined: Fri Jun 25 2010, 08:08AM
Location:
Posts: 143
cool ,thank you. in those condition,what would be the behavior of the diode if the forward voltage rise above the rated breakdown voltage of the diode?
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
It won't, not with practical dA/dt values.
I've seen one paper which used a tapered stack of diodes in forward conduction for pulse sharpening but they started with a ns rise time to begin with.
PS. forward recovery is not purely inductive ... also fast recovery diodes actually have worse forward recovery.
Registered Member #2941
Joined: Fri Jun 25 2010, 08:08AM
Location:
Posts: 143
my concerns was about the possibilities to use the mosfet intrinsic diode to bypass the mosfet in case of negative pulse echo from a coax(we are talking about a mosfet base pulser on a coax load..)
some time the load can create harmonic with rise time of one or two ns .
Registered Member #1875
Joined: Sun Dec 21 2008, 06:36PM
Location:
Posts: 635
Some MOSFETs have good diodes, some not so much. If the S-D voltage gets too high, the MOSFET can probably avalanche it but it could cause problems. If the diode's speed is slower than the FET's fall time, then you may want to consider an external diode and perhaps even isolation of the internal one.
If you can afford a bit more turn-on loss perhaps you should add a capacitor across the switch in the order of perhaps a couple dozen pF to help lower the harmonic spike. Or you could slow the turn-off time to perhaps a similar effect.
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
Forward recovery is not so much a question of speed, it's a question of duration and magnitude. Conduction is defacto instant, they just start at relatively high resistance (10s of ohm, with fast recovery diodes having a higher resistance that standard recovery diodes).
Registered Member #2941
Joined: Fri Jun 25 2010, 08:08AM
Location:
Posts: 143
it make sens... pinky's do you have any reference about this paper you are talking about? (tapered stack of diodes in forward conduction for pulse sharpening) (out of curiosity..)
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
cedric wrote ...
it make sens... pinky's do you have any reference about this paper you are talking about? (tapered stack of diodes in forward conduction for pulse sharpening) (out of curiosity..)
My computer with a million randomly downloaded papers is momentarily down, I'll track it down next week.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
diode recovery
