- Simple "LED driver" chip?
- Posted by Spehro Pefhany on April 9th, 2006
On Fri, 07 Apr 2006 07:39:59 -0700, the renowned "Richard H."
<rh86@no.spam> wrote:
No, AFAIK. Look at distribution quantities-in-stock and prices or ask.
There are thousands of part numbers which will work, and dozens which
are close to optimal depending where the product is being built and
how many. For low to moderate quantities in North America you can't go
far wrong using MMBT4401/4403 for NPN/PNP. Google for data sheets,
there are many, many manufacturers.
'Digital' transistors (transistors with base and maybe E-B resistors
built-in) and digital transistor arrays were developed originally in
Japan by Rohm and are now multiple sourced & are very popular in
consumer goods, but generally not quite as cheap and easily available
as resistors or resistor networks and discrete parts in low
quantities. Generally the transistors 'inside' are referenced to
popular Japanese discrete transistor part numbers.
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
- Posted by Rocky on April 9th, 2006
Spehro Pefhany wrote:
The 2N7002 may be a good fit. FET with low threshold voltage and low on
resistance.
Regards
Robert
- Posted by Richard H. on April 13th, 2006
Rocky wrote:
Indeed, this looks very promising. In particular, ON Semi's version in
a tiny 1.6mm SC-75 package for 4 cents.
After wallowing a while in Digikey's search engine, I tried a different
approach... I jumped over to ON Semi's site and sorted by price
(something Digikey won't do). Thinking I'd work my way up the price
list, I stopped after the first entry, which was a 2.7 cent 2N7002.
Good enough for my purposes, but the smaller version was worth the extra
penny. :-)
Cheers!
Richard
- Posted by Andrew M on April 13th, 2006
"Richard H." <rh86@no.spam> wrote in message news:31m%f.426$AB3.11@fed1read02...
Depending where you have stuff manufactured, the LED-specific constant current drivers
are likely to be cost-effective against the loading and procurement cost of all those
discretes, and the reliability issues surrounding so many parts. Part prices are only
part of the picture.
They're damn easy to use too.
-Andrew M
- Posted by Rich Grise on April 13th, 2006
On Thu, 13 Apr 2006 16:38:45 +1000, Andrew M wrote:
Where do you get one? The last time I checked for a constant-current diode
(AKA "field-effect diode") they were about five bucks a pop!
Thanks,
Rich
