So far all my research says that 5V is the lowest voltage you can use to fully switch off a P-channel MOSFET (like this one http://www.digikey.com/product-detail/en/DMP2305U-7/DMP2305UDICT-ND/2052810), unless you use a driver etc. Or is there one out there that I'm missing?
Thanks as always.
I wouldn't say that one doesn't exist, but I don't know of one, and if they do they would likely be fairly expensive. You best option is likely to use a transistor to switch a higher voltage for the MOSFET.
Why stop at 3.3 V, Vishay has a lot of them for even as low as 1.2 v.
Special applications
2.5 V rated on-resistance (255)
1.5 V rated on-resistance (52)
1.2 V rated on-resistance (19)
Neat! Thanks!
You misunderstand how a p-channel MOSFET works. The threshold voltage is the voltage from gate to source. The source is wired to 3.3 volts so to turn off any enhancement mode PMOS it is standard to set the gate to 3.3 volts.
Turning off a PMOS is easy, turning it on to match datasheet conditions is harder.
You said "fully switch off a P-channel MOSFET".
Just set gate voltage equal to source voltage.
AmbiLobe:
...The source is wired to 3.3 volts...
...Just set gate voltage equal to source voltage...
I'm sorry if I wasn't clear on that. My gate voltage is 0 or 3.3V (from a 3.3V Arduino GPIO pin). My source is 12V (supplying power to a LED bank).
magagna:
AmbiLobe:
...The source is wired to 3.3 volts...
...Just set gate voltage equal to source voltage...I'm sorry if I wasn't clear on that. My gate voltage is 0 or 3.3V (from a 3.3V Arduino GPIO pin). My source is 12V (supplying power to a LED bank).
Aha, this is completely different from the impression given by the name of the
thread. If the supply is 12V, then you can use any regular MOSFET, and the
"3.3V P-channel MOSFET exist?" is immaterial.
The problem you have is to switch the gate of the MOSFET between 0V [on]
and 12V [off] using a 0..3.3V signal. For this you will need a level-shifter
device, such as an NPN inverter as shown here,
