> > I'm driving 12V LED load
>
>
> =3D LED strip - 3 LEDs in series + internal resistors.
>

The internal resistor can be replaced by a npn BJT transistor in
common-collector
setup:
a)  the BJT collector to +12V rail,
b)  the BJT emitter to "+" of the 3 LEDs chain;
c) "-" of the 3 LEDs chain to ground;
d) the BJT base to the Arduino's DAC (the DAC should output up to +12V
rail, or some rail-to-rail amplifier is needed);

The internal resistors normally takes 2 volts or so at full load, that
gives 0.27W heat dissipation at 0.135A. At lower currents the voltage does
not rise dramatically due to the nature of LEDs. So it looks safe to assume
that MAX power on the BJT would be about  0.3W even when the BJT is driven
by DAC, not PWM. With PWM it's not easy to satisfy RF regulations if the LE=
D
strips and wires are long.
--=20
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