Hi Dwayne, can you expand a bit on the parasitic oscillation?  I use=20
NFETS for PWM switching (LED lighting control) often and while I have=20
not seen this problem that I'm aware of, I'd like to know more.

Adding a series resistor of course slows (somewhat) the switching speed,=20
which is paramount in some of my applications.  A ferrite in theory=20
shouldn't affect it much.

What kind of usage would bring about the problems you've seen?

Thanks!
J


Dwayne Reid wrote:
> At 07:06 AM 8/5/2013, John Ferrell wrote:
>> As a hobby/academic level user I try to minimize the different types of
>> parts I keep in my personal parts inventory. I frequently parallel
>> transistors (with matched emitter resistors) to gain more power
>> handling capability. The question: Can I do the same with Fets?
>> especially 2N7002's? Is their a need for the load balancing
>> resistor? In the drain lead?
>
> In general, no ballasting resistors are required when paralleling
> MOSfets, especially if they are functioning as switches.  Its a
> different situation if the FETs are running in the linear region - I
> generally tend to match Vgs on the FETs that are paralleled if the
> FETs are run in the linear region.
>
> I would have NO problem directly paralleling several 2N7002 FETs for
> a switching application.
>
> Do be aware that you might need to install a low-value resistor (100R
> or so) in series with (or a ferrite bead onto) the Gate lead of each
> FET - these serve to eliminate parasitic HF oscillation.  I now do
> this as a matter of practise after being burned in the past.
>
> dwayne
>
--=20
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