Re: Paralleling FET's

On Sun, 17 Oct 1999 19:32:00 -0600 Tesla List <tesla-at-pupman-dot-com> writes:
> Original Poster: "Antonio Carlos M. de Queiroz" 
> <acmq-at-compuland-dot-com.br> 
> Bryan wrote:
> > To put FET's in parallel, you have to find out each one's turn on
> > information exactly.  Then you have to put equalizing resistors in 
> the
> > gate so that they all turn on at the _same_ time and the _same_ 
> amount.
> FETs don't drain DC gate current. 
I know, but a large resistor will still have a effect(a small one, but
enough for equalization), especially for high frequency(when the gate
capacitance's of a power mosfet matter, I think).

Most power MOSFETS can be directly
> connected in parallel without equalizations systems, because they
> conduct less if they become hot. 
I don't think the negative temp coefficient is very significant in this

You equalization method is 
> applicable
> to bipolar transistors, 
but it would be safer to put equalization 
> resistors in series with the emitters. 

You can also put equalization
> resistors in series with the sources of MOSFETS, 

Yes, but then you need higher(therefore more expensive)wattage resistors

but this is usually
> not necessary.

> Antonio Carlos M. de Queiroz

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