[R-390] in rush current limiters

[Jim Shorney]

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On Sun, 22 Dec 2002 19:47:34 -0500 (Eastern Standard Time), Helmut
Usbeck wrote:


>> Question, then: what is the regulating current of this curious tube?
>
>It's not a tube, it's basically a FET diode.  They come in differant
>values but not as high as .3 amps which is what is needed.


I was referring to the original ballast tube, not a solid-state
replacement.


>> Three-terminal regulators can be configured as constant-current
>> devices.
>
>I know and what it's being used for is overkill.  Why reconfigure a
>voltage regulator, three- terminal current regulators are also around.


Why?  Because they're cheap and common as dirt (I've got a ton of them
in my junque box, including a couple of odd voltages, adjustable, and
LDO); and because their behaviour is well documented and understood,
including the need for adequate bypassing.  One resistor of the proper
value is all you need to make it a CC source.  How it behaves with
half-wave rectified AC is another question, however...

- --
Jim Shorney      -->.<--Put complaints in this box
jshorney@inebraska.com
nu0c@amsat.org
Ham Radio NU0C
Lincoln, NE, USA
EN10PT
http://incolor.inetnebr.com/jshorney/
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