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-   -   4A bias on a IRFP240n??? (http://www.diyaudio.com/forums/solid-state/41092-4a-bias-irfp240n.html)

AudioGeek 17th September 2004 03:16 PM

4A bias on a IRFP240n???
 
Is it ok to run a IRFP240n at 24vdc and 4A bias? Is this too close to max dissapation?

Should I run 2 of them in parallel??

They are connected as source follower into a 1:1 output transformer.

Thanks!!

Lars Clausen 17th September 2004 03:27 PM

You are dissipating 100 Watts into a single device, which is pushing it to the limit. If you have a very large heat sink (that will not get more than 50C hot), and it is anodized so you can mount the IRFP without insulation, then it is possible.

Else i would use 2 in parallel.

Cheers

Lars

AudioGeek 17th September 2004 04:04 PM

i keep frying them...
 
hmm... i seem to keep frying them... dunno why.

bias is fine...

perhaps I should fuse them.... duh!

or run them lower current during testing.

Lars Clausen 17th September 2004 04:09 PM

Did you mount them with a MICA insulator?

Nelson Pass 17th September 2004 06:15 PM

At 100 watts you can expect to lose the regularly. I try
not to exceed 50 watts.

sajti 17th September 2004 07:10 PM

I used IRF520 with 30W dissipation. It was not so reliable. I guess to use the IRFP240N up to some 50-60W. If You need more, try to use IRFP260N, which is rated to 300W@25C...

sajti

Lars Clausen 17th September 2004 07:20 PM

Audiogeek: Are you sure it's IRFP240N ??
This device doesn't seem to exist.

AudioGeek 19th September 2004 01:09 AM

it was an IR part... obselete now i think.

so if I wanted a device that would handle 80W.... recommendations?

sajti 19th September 2004 08:24 AM

Quote:

Originally posted by AudioGeek
it was an IR part... obselete now i think.

so if I wanted a device that would handle 80W.... recommendations?

Try to get TO-3 device. That can handle more power, and accept higher temperature. Or try IRFP260N, which is rated to 300W at 25C. Mount them without insulator, and insulate the whole heatsink. And You have to use separated heatsink for each device! Fan cooling is good solution for it.

sajti

Lars Clausen 19th September 2004 09:42 AM

AudioGeek: OK, my suggestion is to use the IRFP250N, and mount it on a black anodized surface without insulator (but with thermal grease). It will withstand easily the 100 Watts of dissipation, if the heat sink stays below 70 C.

IRFP150N will also do nicely. but IRFP250N is the cheapest device.

:)


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