MOSFETs with built in reverse current diodes

[stube40]

Alot of MOSFETs come with a built-in diode across the source and drain. The attached diagram outlines what I mean. I would like to confirm that the purpose of this diode is to allow the MOSFET to handle reverse current to flow.

I know this question might sound really dumb, but I'm not an electronics expert.

Further, if this is indeed the case, is it possible to exploit this diode to enable the MOSFET to allow reverse current in an application where we expect regular reverse currents?

Finally, which particular parameters in the data sheet for a MOSFET describe the diode's maximum reverse current and how long it can maintain this current for?

[indulis]

The

[stube40]

I see -  thanks for the clarification. So, if I want to protect the diode against reverse current I'm guessing I should use an external diode across drain and source, possibly a schottky?

My other thought was maybe to use a 2nd MOSFET connected in parralel to the 1st and in reverse, then sequence the gates of the two MOSFETs so that neither of them ever see reverse current (assuming I know when the reverse current will happen).

Saying that, i prefer the idea of an external diode if that would work.

[KevinIV]

The reverse diode, I'm guessing, could be an indication of polarity. In a DE MOSFET, 0 Vgs provides better conduction at the source than at the drain with the intended Vds polarity. An opposite polarity Vds apparently conducts better. Sometimes doped silicon pieces are used for electrical contacts.