# Selecting a logic level MOSFET compatible with 3.7V power source

Continuation of prior question: Logic level mosfet to switch on 3.7v battery

I am a 'mature' entrepeneur Arduino level electronics noob, apologies. Want to build a flashing alert using 3W LEDs in parallel powered from a 3P 18650 (3.7V) battery pack. I think I have crude solutions using LEDs in series and a 3S battery pack, but not appealing due to uneven LED performance in series configuration, and problems with charging a 3S (balancing, access to 5V/USB charging solutions).

The last answers/comments recommended then un-recommended a P-channel MOSFET, specifically the FQP27P06, because the max Vgs(th) was too high at 4V. In 'fun with sparks' websites I found the Fairchild NDP6020P as an alternative. Finally my question. The Vgs(th) for this MOSFET is -0.4 min to -1 max. Seems like this would be exceeded when I'm using 3.7V source. Consequence, could be MOSFET destruction up to small burst of shrapnel, counterproductive for a safety invention. I read about protecting with a Zener diode and series resistor, but that seems complicated and also primarily designed for surges and polarity reverses.

Kinda yes or no, am I going down the right road with the Fairchild NDP6020P? Bonus points for continuing my education, and much appreciated.

• How do you want LED power to be regulated as 3.7 drops to 3.1V and LEDs only need what 2.9V? Give LED link to datasheet. Otherwise this question may be irrelevant Jan 24, 2018 at 21:43
• Sorry. Chinese LEDs. 2-2.4V forward voltage, 400-500 mA. 6 in parallel with low ohm resistor. Jan 24, 2018 at 21:51
• hmm so 6x 1W in parallel = 6W not 3W but is that at 3.7V Vbat or 3.1V Jan 24, 2018 at 21:56
• Noobie replies, no, 6 ea 3W LEDs in 1 at a time parallel. Made up a 3P battery pack using 18650 batteries, so nominally 3.7V but could go to 4.1V fully charged. Jan 24, 2018 at 21:59
• erhm no . 2~2.4V forward voltage, 400-500 mA. 2x0.4 = 800mW , 2.4x0.5=1200mW avg 1W and LiPo drain to 3.1V what then? Jan 24, 2018 at 22:01