On Thu, Sep 1, 2011 at 11:25 PM, Kerry Wentworth <
kwentworth@skunkworksnh.com> wrote:

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

Do they also block in both directions when off? Or do they only block with
the inherent diode, blocking drain to source?


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

No negative voltages are expected with respect to ground. All positive.

I'm going to conduct a maximum of 2A in either direction. I'll choose the
MOSFETs accordingly. The "solid state relay" is going to be used to control
the charging/discharging of a battery pack and will need to conduct in both
directions and it's relative position between "high side" and "low side"
will therefore dynamically change based on whether the battery is charging
or discharging.


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

So I guess I'll need to use two MOSFETs back to back. The problem with that
is, what do I connect the common "source" pins to? I can't connect them to
GND, because then the current will be shunted to GND when the MOSFET is on,
instead of going through the two MOSFETs.
--=20
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