I thought about using a depletion mode FET to make a 2mA current source..
Gee.. Not many surface mount depletion mode FETs to chose from on Digikey.. Less than a dozen in stock.
Example
Any other(better?) ways to make a 2 component or 1 component 2mA current source?
Conditions Vacross = 10Vdc to 170Vdc f=120Hz T=25C I Error
"D from BC" schreef in bericht news: snipped-for-privacy@4ax.com...
There are some types of three legs, adjustable high voltage regulators out there (LR8 for instance (if memory serves)) that may do the job with one resistor.
petrus bitbyter
apart from the max 100V cr200
-Lasse
Something to look at
I came across this while looking for something else.
Switchable Current Regulators
Features
Minimum of 900 V breakdown
Resistor programmable current source
40 W continuous dissipationInternational standard packages JEDEC TO-220 and TO-252
On/Off switchable current source
IXCP10M90S
Did not look for SM equivalent...Supertex DN345 has an Idss of 200mA; about 2.6VGS for current source so 2mA or 20mA is easy; 2 parts: resistor and depletion mode FET.
....or maybe the SM version of the Fairchild J202; one part; ntg on voltage.
3_0...
mA;
Have you looked at Supertex's web site lately :< :< :<
Also
3_0...
Sorry about the previous blank post! There are lots of SMD junction FETS available. The vast majority of JFETs are depletion mode. The problem is the breakdown voltage. You may have to add a resistor- Zener combination to protect the FET. Also, Linear Systems
IXYS has a good selection of HV current regulators requiring only one external resistor. The problem might be in finding them at a distrubutor.
Here take your pick. HV current regulators top left menu.
Start-up resistor replacement for an off-line SMPS?
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com
...that was supposed to be DN3545...
....but....but....Mouser seems to carry them...DN3545
** That gives 1mA...try something near 5.8K... ...or the Fairchild J202..
_R3_0...
Perhaps Mouser will have them right up until you order them for production. When a company makes something hard to find on their web site, it is time to stop designing the part in and time to start designing it out.
If a company makes everything they make hard to find, it is not just time to design all those parts out. It is time to sell the stock.
I'm designing the startup for an smps.
D from BC myrealaddress(at)comic(dot)com BC, Canada Posted to usenet sci.electronics.design
I'm still following this thread. I made some replies but they didn't show up. It's mysterious... (It could be that I've messed up something.) Only today are my replies now appearing.. However, my internet service has been acting erratic. And now I'm too busy to make replies :(
D from BC myrealaddress(at)comic(dot)com BC, Canada Posted to usenet sci.electronics.design
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