--===============0356334639==
Content-Type: text/plain; charset=GB2312
Content-Transfer-Encoding: quoted-printable
X-MIME-Autoconverted: from 8bit to quoted-printable by pch.mit.edu id m4DED4Pj016037

Hong,

The gate resistor is always trial and error - it depends on the layout.
Strongly. Try 10 ohms first, observe the gate voltage at the FET. If it
does not ring at the flat spot, reduce the resistor value. If it rings,
increase the value. Ringing usually indicates distorted drain voltage
rise or fall, increased loss.

Then, if you have a stable load and source, and time to wait for
temperatures to stabilize, tune the gate resistor value for minimum
loss. That's what you are really seeking.

Tom Stamm

*******************************************
*******************************************
*                                         *
*         NOTE: NEW EMAIL ACCOUNT         *
*  PLEASE REPLY TO tastamm@sbcglobal.net  *
*                                         *
*******************************************
*******************************************

Work: 847-585-3092 9:30am-6:00pm
Home: 773-631-5399 weekdays 7:30pm-10:30pm
                   weekends 10:00am-10:30pm


gardenyu wrote:
> =20
> =20
> Hello
> =20
>      I have some IRF 3205 fets at hand, this is a slow one, its gate ch=
arge is about 40nC. Since I need to increase the switching frequency to a=
bout 100k Hz, thus I need a strong enough gate driver chip to deliver a b=
ig current, thus switching loss will not be a too big problem.
>      I also need a disable pin on the gate driver chip for safety issue=
 if possible.
>      There is a tradeoff between price and performance, as I have found=
 some processor oriented fast chips and weak ones, have you ever found a =
design guide for gate driver IC, including how to find a suitable gate re=
sistor, etc?
> _________________________________________________________________
> Windows Live Photo gallery =CA=FD=C2=EB=CF=E0=BB=FA=B5=C4=B3=AC=BC=B6=B0=
=E9=C2=C2=A3=AC=C7=E1=CB=C9=B9=DC=C0=ED=BA=CD=B1=E0=BC=AD=D5=D5=C6=AC=A3=AC=
=BB=B9=C4=DC=D6=C6=D7=F7=C8=AB=BE=B0=C3=C0=CD=BC=A3=A1
> http://get.live.cn/product/photo.html
>=20

--===============0356334639==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Disposition: inline
Content-Transfer-Encoding: 7bit

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

--===============0356334639==--