> 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.

It sounds like you are using the wrong FET.  The IRF840LC has 850mOhms when
full on, and also can't handle your 12A current continuously.  At 12A, 10%
duty cycle, and 850mOhms, it will dissipate just over 1W.  Nowadays you can
get FETs with much lower on resistance.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body