MOSFET Gates and cooling

[strokedmaro]

Im new to MOSFETS (1st time using them) and was curious about a few things. I recently received 4 of these:

Digi-Key - IRF3711ZPBF-ND (International Rectifier - IRF3711ZPBF)

My first question is why does it have two drains? Just because? I also see that some of the surface mount MOSFETS have drain PIN cut off...could I do that also? Some datasheets also give dimentions for the circuit board area the drain is soldered to (the larger pad) for cooling...on the data sheet for these IRF3711's there is no information about that (even for the surface mount kind) How would you figure that out.

Finally this MOSFET has a hole which Im assuming could be simply screwed to a heat sink of some kind....could it also simply be soldered to a cb? THANKS

 

[jpanhalt]

My first question is why does it have two drains?

It doesn't. It may have multiple connections to the same drain. I am currently using an SMD mosfet with 4 drain connections on a 6-pin package. The datasheet will tell you whether they all need to be connected to the circuit, but probably not.

Just because? I also see that some of the surface mount MOSFETS have drain PIN cut off...could I do that also?

Yes. I have removed the drain pin and made the connection to the tab of TO-220 mosfets. That was done for heat sinking.

Some datasheets also give dimensions for the circuit board area the drain is soldered to (the larger pad) for cooling...on the data sheet for these IRF3711's there is no information about that (even for the surface mount kind) How would you figure that out.

You might use data from another device to calculate the heat dissipation per sq. cm from your PCB, then apply that information to your device.

Finally this MOSFET has a hole which Im assuming could be simply screwed to a heat sink of some kind....could it also simply be soldered to a cb? THANKS

Yes, if you mean the hole in the metal tab of the drain connection. Probably not, if you are referring to a hole in the plastic body of the mosfet. Also, you must determine from the datasheet whether the tab is the drain or is insulated.

John