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Newer Power FETs

PostPosted: Sat Apr 09, 2011 3:59 pm
by Tom WA3KLR
Steve WA1QIX mentioned a new FET on the AM Forum board recently – the CMF20120D silicon-carbide 1200 Volt MOSFET:

I have been inactive on this board for several years, but I try to keep an eye on new FETS. Here are some other newer FETs of the last 2 1/2 years or so that may be appealing also. They are normal price range and all three of these are 600 Volt
N-channel power FETs, TO-247 style of package, and have “good drive efficiency”/low gate charge for their size:

ST STY60NM60 RDSon 0.065 Ohm, Id 60 Amps, Qg = 178 nC.

Fairchild FCH35N60 RDSon 0.079 Ohm, Id 35 Amps, Qg = 139 nC.

ST STW20NM60FD RDSon 0.26 Ohm, Id 20 Amps, Qg = 37 nC.

Re: Newer Power FETs

PostPosted: Thu Apr 21, 2011 4:44 pm
by Tom WA3KLR
I have updated a list of FETs I tested 4 years ago with the 3 newer ones above. The list ranked the power FETs according to ease-of-drive; the higher the Rule of Thumb number the easier the FET is to drive.

Go to this AM Forum topic to see the updated list : ... #msg209862

Re: Newer Power FETs

PostPosted: Fri Nov 18, 2011 11:23 am
by Tom WA3KLR
Friday, November 18, 2011 Update

The latest interesting FET I spotted in September, appears to be faster switching than previous FETs. So this could be a real good choice for 40 meters. It is made by IXYS and the data sheet I have (March 2011) is labeled “Advance Technical Information”. It is available from both Digikey and Mouser for $11 each. I have not ordered any.

But the part is:

Polar3 HiPerFET 600V, 64 Amps, Rds(on) = 95 milliOhms, Qg(on) = 145 nC.

IXYS IXFK64N60P3 TO-264 package
and IXFX64N60P3 PLUS247 package.

My “Rule-of-thumb ease of drive number” based on this part's data sheet calculates to 58, which means it is relatively easy to drive for it’s size compared to most other power FETs.

* 11/19 - Here is the link to the IXYS overview sheet on the design of their new PolarP3 FET family: ... _final.pdf

Re: Newer Power FETs

PostPosted: Fri Nov 18, 2011 11:01 pm
by Gilly
Hi Tom

You certainly have done quite a bit of testing to come up with all this information .... very handy to know as 40M is more difficult than 160/ get things going with high efficiency.....
This is by my experience anyway ... my output balun / transformer does get warm to hot depending how much power I push it to....

In Australia our power levels are quite low compared to yours ..... 120Watts Carrier modulated to appox 100% :mrgreen:
So efficiency is not all that of an issue...only personnal satisfaction.....

The FETs I use now are the 11N90 / C's and IRF840s .........

Those you mentioned have not come across and would probably need to be imported etc:


Re: Newer Power FETs

PostPosted: Mon Nov 28, 2011 7:45 am
by Diego-CX4DI
I got exelent perfomance in 40M using the APT's : APT5024BLLG.

some test at


Re: Newer Power FETs

PostPosted: Fri Dec 23, 2011 4:53 pm
by steve_qix
The lower voltage FETs are *ALWAYS* easier to drive, and may even be faster.

However, the distinct and ever-present disadvantage is that you must reduce the high voltage supply significantly to keep a reasonable safety factor. For instance, if using a 600V MOSFET, the high voltage power supply must be reduced from 130V to 85V to maintain the same safety factor as is afforded by an FQA11N90 and a 130V (45 volts at carrier) supply.

With a 600V MOSFET, you could expect to be able to run about 30 volts at carrier, with an 87V total supply voltage and NO MORE than that.