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Need Some 1mA Current Limiting Diodes... Help!

Started by Paul Marossy, February 04, 2005, 12:56:00 PM

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Paul Marossy

February 04, 2005, 12:56:00 PM
I need some 1mA current limiting diodes similar to these: http://www.centralsemi.com/leadedpdf/ccl0035%20v2.pdf

Anyone know of a source for these types of diodes? I need some to make a module for my Seymour Duncan Convertible...
http://www.diyguitarist.com/GuitarAmps/SD-Convertible/HG-Hybrid.htm

The usual sources like Mouser don't seem to have these.  :(

Peter Snowberg

#1
February 04, 2005, 01:00:27 PM
You can make such devices with a JFET and a resistor. :D

http://www.vishay.com/document/70596/70596.pdf

Google for JFET "current source" for lots more.
Eschew paradigm obfuscation

luix

#2
February 04, 2005, 01:01:54 PM
You can try to use a JFET as a constant current diode....

Vsat

#3
February 04, 2005, 01:42:47 PM
Not made anymore, but if you can find them, the Motorola MCL1301 is a 1 mA diode. It is also possible to use a LM317 regulator (the mini TO-92 version is convenient) as an adjustable current source. Might/might not be suitable for your application.
Regards, Mike

Paul Marossy

#4
February 04, 2005, 02:18:57 PM
Peter-

Thanks for that interesting link. I don't think that I have enough room in that little module to fit all of the things required to do a FET constant current arrangement because I'll need some way to bring down the B+ voltage (big resistor?) from ~300V to ~30V in addition to the actual FET circuit. It might fit, I dunno. If it does, stuff will be crammed in there...

Vsat-

Definitely not enough room for a LM-317 and everything that goes with it. I guess that leaves me with trying to find an MCL1301 if there's not a practical way to modify my module. I did write to CentralSemi, and they said that they would send me some leaded 1mA current limiting diodes, but I haven't seen them and it's been probably 3 weeks since I was told that they would send me half a dozen free of charge.  :(

EDIT: A couple of years ago, I was trying to determine what a CIL1301 diode was before I finally recently asked Kevin Beller at Seymour Duncan what it was. Anyhow, some people at Ampage thought that a 1N914 might work and some people thought it would fry or not work like intended. I tend to agree with the "it won't work" camp. Any thoughts?

Johnny G

#5
February 04, 2005, 05:46:28 PM
well even tho its probablly not the best answer. whats the worst that could happen. if there are 2 diodes there then thats 2 ma (wow my maths lessons paid off). so why not put a couple 1n914s in there and find some way of measuring the current through them. it something goes funky then at worst you might burn out the tube and the diodes. wouldnt any diodes that limit it to 2ma be fine?
LET US INSTIGATE THE REVOLT,DOWN WITH THE SYSTEM!

Peter Snowberg

#6
February 04, 2005, 06:57:30 PM
Current limiting diodes are not simple PN junctions so you can't substitute a 1N914. They are both diodes.... but it's like a cheese sandwitch and a scrap metal sandwitch..... they're both sandwitches. ;)

A single JFET and a single resistor should be able to get a reasonable substitution happening.

Paul, you mentioned 300V? Is the diode in the plate or the cathode part of the circuit? I've seen constant current diodes used in long tailed phase splitters a number of times. In the cathode position the voltage is suitable for 30V devices.
Eschew paradigm obfuscation

Paul Marossy

#7
February 05, 2005, 10:30:52 AM
Peter-

Well, looking at that application note, it appears that the FET needs a 30V power supply to do its thing. That would make things more complicated.

But, I just did a quick lookover, I will have to look at it closer in the next day or two.  8)

zachary vex

#9
February 05, 2005, 04:01:42 PM
i've successfully used J201 fets as current-limiters way up to 75 volts.  i've put two in series for double that... i figure you can put as many in series as you need.

zachary vex

#10
February 05, 2005, 04:10:38 PM
okay, i looked up my notes, and using a J201 with the drain connected to +4.5-73 volts, the gate and source shorted and connected to the anode of a high-brightness led to ground, i got .85 mA continuously.  by adding a second J201 in series (also gate/source shorted) the current moved a little bit around 73-75 volts and then restabilized for another 75 volts or so.  you can theoretically set up 5 J201s in series for about 1 mA of regulated current using a 300 volt supply.

Peter Snowberg

#12
February 05, 2005, 05:45:11 PM
I wonder how those things would be for ground-shunt style clipping diodes with some series resistance? :D
Eschew paradigm obfuscation

zachary vex

#13
February 05, 2005, 10:06:47 PM
the J501 is $1.73 each/100 pcs at mouser.  seems like the j201 is $0.25 for one extra lead.  8^P

Paul Marossy

#14
February 05, 2005, 11:38:12 PM
Quoteyou can theoretically set up 5 J201s in series for about 1 mA of regulated current using a 300 volt supply

Hmm... I may have to give this a try. Thanks for all of the suggestions guys.   :)

QuoteI wonder how those things would be for ground-shunt style clipping diodes with some series resistance?

Joe Davisson's "Amber Boost" used some 2N7000 (I think) MOSFETs as clipping diodes. I don't remember any series resistance, though.  And it used a CMOS opamp, too. It sounded pretty good to my ears.  8)

ragtime8922

#15
February 07, 2005, 08:22:54 AM
I have a similar problem. I've been wanting to build Steve Bench's LVPS (low voltage power supply) that gives you 160VDC from a 12V wall wart without the use of a transformer.

http://members.aol.com/sbench101/PowerSupplies/lvps.gif

It calls for a PS304R 3A, 400V Fast Recovery diode. Where do you get this or how do you fabricate it?

zachary vex

#16
February 07, 2005, 08:36:02 AM
maybe a mouser 583-SF16 would do.  it's not as high-current, but maybe using it as a starting point you could find a substitute.

ragtime8922

#17
February 07, 2005, 11:22:01 AM
Quote from: zachary vexmaybe a mouser 583-SF16 would do.  it's not as high-current, but maybe using it as a starting point you could find a substitute.

Thanks again Zachary. Have you seen my thread on the "12v to 160v, where would you tap to get the 6.3 filament" question? Also, I guess I always thought that filament voltage had to be AC. Now I hear that DC is better because of the ability to reduce or eliminate AC hum. Any suggestions? Anyone?
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