Re: MOSFET driving

Frederic wrote:

Hello everyone,

I'm a bit confused about the use of a small series resistor at the gate of a power MOSFET. I've seen this in some schematics.
I have the gate of a IRFD120 MOSFET pulled up to 13V (with respect to source) with a 100K resistor. This gate is then pulled down by the "discharge pin" of a TLC555 (CMOS version of a NE555), in few hundred nanoseconds at most.
Is a small resistor needed in series with the gate? What's the purpose? Which value? How is it calculated???

Fred


that's a common method used to remove parasitics
sort of lowers the Q in the circuit among other
things like, help saving some major components if an
attached component fails and could cause over drive for
which the R could take the heat instead.
there are to many reasons popping in my head at the moment.
it simply depends on the application.
Another one is to reduce High freq noise..
i'll stop now.



--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

.

Relevant Pages

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    ... I have the gate of a IRFD120 MOSFET pulled up to 13V with a 100K resistor. ... Such a series resistor is often needed when the gate is driven by a very low impedance source that doesn't damp the resonance created by the gate to drain capacitance and the lead and trace inductance. ...
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  • Re: MOSFET driving
    ... I have the gate of a IRFD120 MOSFET pulled up to 13V with a 100K resistor. ... Such a series resistor is often needed when the gate is driven by a very low impedance source that doesn't damp the resonance created by the gate to drain capacitance and the lead and trace inductance. ...
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    (sci.electronics.design)