Electronics > Projects, Designs, and Technical Stuff
Constant Current LED Driver - BJT
zitt:
I usually use one LED + Resistor + BJT in diode mode to set the LED current... then use only a BJT to drive the remaining LEDs.
IF there is enough supply voltage on the BJT side; I use two or more LEDs in series to the collector and attach directly to V+.
That said; I do tend to put a current limiting resistor on the final BJTs just to limit the Power dissipation in that BJT.
http://pinball-mods.com/blogs/?p=452
Benta:
Remove R2, replace R1 with a second 1N4148. You'll have ~0.65 V over R3.
mariush:
My question is why, just to learn or for an actual application?
There's loads of simple led drivers out there, from super simple to very advanced ones.
Here's one of the simplest, NSI45015WT1G: www.farnell.com/datasheets/1878366.pdf (others with current preset at various values: https://uk.farnell.com/search?st=NSI* )
Benta:
Well, the OP's costs around 5 cents...
mariush:
--- Quote from: Benta on July 13, 2019, 07:03:43 pm ---Well, the OP's costs around 5 cents...
--- End quote ---
And how much in PCB real estate and pick and place machine time or human time to solder the parts... how much time to bin the transistors for same hFe / other factors?
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