Re: Size of Resistors
- From: "PeteS" <PeterSmith1954@xxxxxxxxxxxxxx>
- Date: 25 Aug 2006 14:00:07 -0700
Jonathan Kirwan wrote:
On 25 Aug 2006 08:31:34 -0700, "GraemeC"
<graeme.cunningham@xxxxxxxxxxxxxx> wrote:
<snip>
This circuit provided a constant current through the load LED (D1) when
Vi1 is greater than approx 3v
<snip>
I've only just begun to look at the arrangement. You have 14 BJTs in
order to provide a constant current into an LED!?? Can you explain a
little more about why?
Jon
I ditto this reponse.
If you are trying to provide 250mA into an LED as a constant current
(which seems awfully high), it can be done with only a single
transistor and a few other parts.
Apart from that, the part you specify (QTLP690C) is listed as obsolete
http://www.fairchildsemi.com/sitesearch/fsc.jsp?command=text&attr1=&attr2=&t=0&i=sitemap+id&ia=1&text=QTLP690C+&as=1&render=1&w=
Please tell us the application requirements :)
Cheers
PeteS
.
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