Yes, FETs parallel better than BJTs, you don't need emitter resistors,
watch the gate drive though!
Why are the FETs getting hot?
If you are switching 12 amps they should only be about 10 watts.
(Did you forget the external load dump clamp?)
Are you driving the FET enough to saturate it?
Of course the capacitance will double.

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-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of fred jones
Sent: Friday, August 23, 2002 2:55 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: [EE]: Can you parallel FETs?


Hi all,
Once in the past I needed to switch a lot of current so I paralleled a few
BJT power transistors together.  I am currently switching 24VDC through a
coil(a couple ohms) through an IRF840LC FET with an on time of 200us every
2ms (500hz).  The FET gets pretty hot.  I need to increase the on time to
1ms so I anticipate it is going to get extremely hot.  I'm wondering if any
of you with experience can tell me if its possible to parallel FETs to
spread the load?  I'm wondering if the lower capacitance (the LC in 840LC)
will be increased.  Thanks for any wisdom on this.
Fred

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