Re: Paralleling FET's

• To: tesla-at-pupman-dot-com
• Subject: Re: Paralleling FET's
• From: Bryan St <warp27-at-juno-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Mon, 18 Oct 1999 18:20:47 -0600
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

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
case.

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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