I have a 5VDC fan (AUB0505HD), and my ultimate goal is to drive this fan using a 3.3V PWM signal from a Raspberry Pi Zero.
I haven't worked with transistors much outside of EE school, so I don't fully understand how to use them practically. I did some reading, and I came to believe that a MOSFET should help me accomplish this. I went to Digikey and selected a MOSFET that I thought would do what I wanted: ZVN4206AV. I selected this MOSFET because the fan datasheet states that it will need approximately 330 mA at 5V. The threshold voltage on the MOSFET is 3V max, which I thought meant it would fully conduct at 3V, which is perfect because I'll have a gate voltage of 3.3V. As it turns out, after testing, I learned that this is not the case -- the 3.3V gate voltage is only enough to get maybe 1/3 power out of the fan.
Clearly I misunderstood some of the MOSFET specifications. Now, I'm at a loss regarding how I can get the maximum power out of the fan using my setup. Here's my example circuit:
I need the 5.5V regulated power for the Raspberry Pi Zero to operate, so I was hoping to piggy-back off of the regulator on the fan as well. Is this possible, or do I need to step up to a higher voltage for the fan since I'll have voltage drop on my switching components?
I looked at BJTs, and it looks like they will give me a voltage drop of maybe 1V across just the BJT, which is undesirable... Maybe I don't understand something with those as well.
Any help is appreciated.