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 #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
I've had some experience with these, putting a 1K resistor across the diode(s) speeds up switching transitions by discharging the device capacitance of tens of pF.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Conundrum wrote ...
I've had some experience with these, putting a 1K resistor across the diode(s) speeds up switching transitions by discharging the device capacitance of tens of pF.
do you mean a 1K resistor across A and K ? im thinking of using a logic type IC with a series resistor, but a second resistor, means a V divider.
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780
you don't want full-on and full-off
there must still be biasing when OFF (5-10% of nominal current generally speaking) as to be placed just under the treshold, so you throw away the inertial part of the curve, and you achieve better optical pulses
the diode capacitance stays charged, but you modulate current
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Shrad wrote ...
you don't want full-on and full-off
there must still be biasing when OFF (5-10% of nominal current generally speaking) as to be placed just under the treshold, so you throw away the inertial part of the curve, and you achieve better optical pulses
the diode capacitance stays charged, but you modulate current
you are saying 'current', do you mean voltage? keeping the forward voltage drop just barely applied at the OFF condition, so the ON condition can be reached sooner?
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
Patrick wrote ...
Shrad wrote ...
you don't want full-on and full-off
there must still be biasing when OFF (5-10% of nominal current generally speaking) as to be placed just under the treshold, so you throw away the inertial part of the curve, and you achieve better optical pulses
the diode capacitance stays charged, but you modulate current
you are saying 'current', do you mean voltage? keeping the forward voltage drop just barely applied at the OFF condition, so the ON condition can be reached sooner?
Diodes (laser and plain ol light emitting) are driven as constant current devices generally when driving them progresses beyond a voltage source and resistor. The Vf varies with temperature, and from diode to diode, and the V/I curve is rather steep, so a modulated current source would be desirable.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
ConKbot of Doom wrote ...
Patrick wrote ...
Shrad wrote ...
you don't want full-on and full-off
there must still be biasing when OFF (5-10% of nominal current generally speaking) as to be placed just under the treshold, so you throw away the inertial part of the curve, and you achieve better optical pulses
the diode capacitance stays charged, but you modulate current
you are saying 'current', do you mean voltage? keeping the forward voltage drop just barely applied at the OFF condition, so the ON condition can be reached sooner?
Diodes (laser and plain ol light emitting) are driven as constant current devices generally when driving them progresses beyond a voltage source and resistor. The Vf varies with temperature, and from diode to diode, and the V/I curve is rather steep, so a modulated current source would be desirable.
Oh! Duh on my part! yes the V/I curve is what i should be looking at. i see what conk and shrad meant... so if i have the tinyest amout of current conduting at the Vf, then its nearly off.
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.
how fast can cheap lasers be pulsed?
