- the LEDs require high forward voltage V_f > 2.75 V ([ref1]), which is at the limits of the GPIO pins' output V_OH > 2.90 V ([ref2]);
- the LEDs draw large forward current I_f reaching up to 100 mA ([ref1]), while GPIO pins can't source more than 16 mA per pin & 50 mA combined ([ref2]),
we think of using this circuit ([ref3]):
Problem is, a voltage drop of (5−V_C) V across the LED load could exceed the maximum rating of the load V_f_max = 3.40 V ([ref1]).
Could adding resistance R_x before the load help? If so, how can we calculate its value?
More generally, is this circuit appropriate to use? — we're afraid of damaging the Raspberry Pi GPIO pins & are beginners in Electronics.