FETs conduct equally in either direction when on, but you have left out=20
a lot of details.

Is the "high side" going to go negative?  How far negative?
How much current do you expect to conduct?

Some FETs, particularly high current ones, have a diode between source=20
and drain, so although they conduct equally in both directions, the=20
don't block equally in both directions.

Kerry



V G wrote:
> Hi all,
>
> I need something small, cheap, and that behaves like a mechanical relay
> (that is, conduct current in both directions when on, can be placed anywh=
ere
> between low side and high side).
>
> Could I do this with a single N channel MOSFET and place it anywhere betw=
een
> the low side and high side? I plan to drive the gate with a charge pump (=
15V
> or so). The low side voltage is 0V, and the high side voltage shouldn't b=
e
> any more than 5V, so a minimum gate to source voltage of 10V should be mo=
re
> than enough to fully switch on the MOSFET. The question is, will the MOSF=
ET
> conduct in both directions when on and block in both directions when off
> (like a relay)?
>
> I don't really care about isolation or switch times. I just need it to
> conduct in both directions when I turn it on, and block in both direction=
s
> when I turn it off, and be easy to turn on and off (ideally with 3.3V or =
5V,
> but I'll use a charge pump if I have to).
>  =20

--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.