/diy/ - Do It Yourself

>>1218674
>10mA in the maximum ratings is a joke. If not, what would you even use one for?
Precision reference current for data conversion or timer, perhaps?
>30mA and 35mA they're both recommended and maximum
You might get away running both of those at 30mA with minimal loss of brightness. If not, just add one more. LEDs are cheap.
If all the transistors are thermally bonded, the current shouldn't drift more than a few percent, and only toward zero. You could add one transistor per LED if you like.
1 millihenry is probably too big for most switchers, but at 3000Hz that might just work.
You might also look into ICs that are designed just for the purpose of boosting a voltage to a constant current for a series string of LEDs, such as the LM3410, which your local shop may or may not have heard of. Or, adapt a traditional boost converter similar to Pic related, where the desired output voltage is "programmed" as Vfb + Vleds @ desired current. We are getting a bit away from the discretes only rule, I'm sorry.