Mosfet

I'm having an issue picking a good MOS FET for a project. When looking at the datasheets, what am I looking for when it comes to the gate voltage? I need to pick one that I can power either with a pic pin or a npn transistor.

Also, is it safe to run AC current through one?

GatorGnet said:

I'm having an issue picking a good MOS FET for a project. When looking at the datasheets, what am I looking for when it comes to the gate voltage? I need to pick one that I can power either with a pic pin or a npn transistor.

Also, is it safe to run AC current through one?

Click to expand...

Unless it says "LOGIC LEVEL", it requires a gate voltage of 10V to turn it on hard enough to get the advertised ON RESISTANCE. If it does say "logic level", it needs 5V (not 3.3V). If you are running a 3.3V PIC, you will need to do something to get the voltage higher. If doing that, you might as well as use a 10V one, and use a transistor as an intermediate driver.

You cannot run AC because FETs have a "body diode" that would conduct when the drain is the "opposite" polarity.

Here is the one we are working with.

http://www.datasheetcatalog.org/datasheet/irf/irf740.pdf

why dont you use triac? it allows ac.

georgetwo said:

why dont you use triac? it allows ac.

Click to expand...

Just happens to be what we have on hand at the moment.

What kind of load are you switching? Do you have a schematic of your project?


Torben

I'm currently working on a similar project and have not completed this one but it will be a 12vdc 1-10amp load.