mulu:
I am trying to dim an LED strip using an Arduino. It works but I can't dim it very low. I hooked it up to an old scope and realized that the fall time measured at D (between the LED strip and the NDP6020P) is very slow (upper curve on the scope). The voltage at G on the NDP6020P is very quick (lower curve on the scope), though. Why do I see this low fall time and how can I fix it?
That's perfectly OK, your LEDs are a very high impedance load once the current stops flowing, so cannot pull
the drain of the pFET down to ground much. Note that the voltage drops nice and fast from 12V to about 7V,
which is when the LED current drops to nothing... If you had measured the current waveform it would have
looked fine.