[Top] [All Lists]

Re: [Amps] New NXP BLF578XR 1200W LDMOS FET is "indestructible"

To: <>
Subject: Re: [Amps] New NXP BLF578XR 1200W LDMOS FET is "indestructible"
From: "Baruch Zilbershatz" <>
Date: Sat, 23 Jul 2011 02:58:52 +0300
List-post: <">>
Igot 4 devices 2 were 578XR and two had no printing at all on.

    Got them as samples so I have no idea about price sorry.

As far as I can say this device needs cooling.

But all that scary talk about super cooling is a little out stretched ( in
Hebrew it sounds good)

A good sized copper slab  polished to mirror flatness and CLAMPING(!)

The device with another pre shaped copper clamp is my method, works fine
also for MRF6VP11KH,MRF6vp121KH that are similar devices by Freescale but
not as rugged.

All these had been tested and amps were built already.

The issue is not the cooling but the matching of the devices at the output.

At first a heat sink with copper inserts on a regular shape 4 sleeve trafo
was used.

The temp rise of the cores I had was a dead end road.the temp gradient was
too high and I was lucky not to loose the Fet.

I moved to  TLT approach with a ferrite loaded coax at a 1;9 configuration
with a balanced to un balanced 1:1output coax balun with 43 type ferrites
loading it.

Coax lengyh of all sections is 26.4 cm to stay away from the 90MHz upper
limit that was my design goal.

Ferrites should have enough cross sectional area   "meat" in order to take
the temp rise on that coa        x 

I used CK type caps ,many in parallel in the RF pathes since I had no ATC's
with the needed values.



That is just the tip of that iceberg story of my affair with the 578


4z4rb Baruch

Shalom from Israel





Baruch Zilbershatz

Nitzanay-Oz 118

Nitzanay -Oz



phone: (+)972-052 8753838


Amps mailing list

<Prev in Thread] Current Thread [Next in Thread>