[Amps] New solid state kid on the block

Tue Feb 1 09:12:12 PST 2011

BTW, something that might just work: there's a company named Ceramic
Magnetics in cube format with quite a hefty cross sectional area. Never used
them but they may be worth a try, instead of Tomita
Alex		4Z5KS
-----Original Message-----
From: Baruch Zilbershatz [mailto:4z4rb at bezeqint.net] 
Sent: Monday, January 31, 2011 10:59 PM
To: 'alexeban'
Cc: Amps at contesting.com
Subject: RE: [Amps] New solid state kid on the block

True
By the way tomita stopped making the ferrite( large 2 holes)
There is no one else... 

4z4rb 
Baruch Zilbershatz 
Nitzanay-Oz 118 
Nitzanay -Oz 
42836
ISRAEL 
phone: (+)972-052 8753838

-----Original Message-----
From: alexeban [mailto:alexeban at gmail.com] 
Sent: Monday, January 31, 2011 10:46 PM
To: 'Baruch Zilbershatz'; 'Fuqua, Bill L'
Cc: Amps at contesting.com
Subject: RE: [Amps] New solid state kid on the block

A little correction: MRI systems require a VERY linear RF system: they don't
tolerate well a high content of harmonics and/or IMD. This is the reason for
the 100mA quiescent current setting: it allows AB1 operation instead of pure
class B.
As for thermal behavior: these transistor cases were designed for water
cooling: a drilled out heatsink with cooling water circulating inside. We
tried its smaller brother at my last workplace with quite reasonable
results, installed on a copper heatsink made by the George Company with
forced air cooling and they worked all right too.
More problematic is the magnetic cores for the transformers: about the only
company making them is Tomita Electric and they don't exactly shine as to
service consciousness.

Alex   4Z5KS

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Baruch Zilbershatz
Sent: Monday, January 31, 2011 6:42 PM
To: 'Fuqua, Bill L'
Cc: Amps at contesting.com
Subject: Re: [Amps] New solid state kid on the block

I made some tests with that animal.
It is more intended for class c or pulse in MRI systems at class AB it is
not better than the 578 that is for linear work.
Made 2 boards one regular FR4 the other Teflon duroid. Got great results
with the Teflon 
The FR4 got very hot
4z4rb 
Baruch Zilbershatz 
Nitzanay-Oz 118 
Nitzanay -Oz 
42836
ISRAEL 
phone: (+)972-052 8753838

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Fuqua, Bill L
Sent: Monday, January 31, 2011 5:06 PM
To: Manfred Mornhinweg; amps at contesting.com
Subject: Re: [Amps] New solid state kid on the block

Looking at the data sheet. It is intended for class c operation. If you are
going to operate it in AB you will need one heck of a heat sink and low
thermal resistance to the heat sink.
But there is one thing that confuses me. 

Case Temperature 63°C, 1250 W CW, 100 mA, 230 MHz @ RθJC 0.15 °C/W
Ok I understand 1250 Watts output CW with case temperature of 63 degrees. 
 What is the 100mA about?

In class AB the effeciency will be much lower and you would be talking about
much less output also it may be very nonlinear and require lots of negative
feedback
thus reducing its gain further.  In class C at a glance it seems to have
fairly good gain. 

73
Bill wa4lav

________________________________________
From: amps-bounces at contesting.com [amps-bounces at contesting.com] On Behalf Of
Manfred Mornhinweg [mmornhin at gmx.net]
Sent: Sunday, January 30, 2011 5:06 PM
To: amps at contesting.com
Subject: [Amps] New solid state kid on the block

Hi all,

has anyone yet gotten his hands on one of these new kids on the block?

http://cache.freescale.com/files/rf_if/doc/data_sheet/MRFE6VP61K25H.pdf?pspl
l=1

If anybody has tried it, I'm sure there are many of us who would love to
hear about it!

The data sheet isn't very complete, for example it tells essentially
nothing about thermal behavior of the bias. Some experimentation seems
to be in order. My only problem doing that is the price tag of around
USD 270! That should be fine for USING this baby, but not for RISKING it
while developing a stable good circuit!

Manfred.

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