Corvus Post subject: Freescale MRF transistor Posted: Fri Oct 05,
2007 9:19 am Captain Joined: Mon Jul 18, 2005 12:55
pm Posts: 8 Geetings! I am experiencing the sudden death
of lots of PA pallets mounted with MRF377 transistors. Anyone else with
the same problem? I am just wondering if its my own problem or in fact
is an inherent problem with this kind of transistor. People said is
better to change to NXP. Why? Any solution finded with MRF?
Cheers! Top IR Post subject: Posted: Fri Oct
05, 2007 3:04 pm Site Admin Joined: Mon Jun 27, 2005
2:02 pm Posts: 373 Location: Germany Greetings Corvus!
You are not the only one! A while ago I was working on a
PA design which was made of MRF374, and MRF377. I had the same problem
with this series of transistors. Although, as far as I recall, the problem
was with the MRF374. In my case the problem was that MRF374
was used to drive another MRF374 and the amount of input power to the
second MRF374 was too high. This series of transistors doesn't have
a device with an intermediate output power level in the range of 60-80W
in contrast to the UMTS line where the variety of devices is much larger:
MRF21010, MRF21030, MRF21045, MRF21060, MRF21090.... The problem
in essence has to do with a protection diode that is located between
the Gate and Source. This diode is meant to protect against reverse
voltages. The malfunction happens during a high voltage RF swing, which
causes the diode to clamp the negative part of the cycle, as a result,
a short-circuit is caused between the Gate and Source. I had to change
a lot of transistors until I switched to another manufacturer.
Top Corvus Post subject: Posted: Mon Oct 08, 2007
5:56 am Captain Joined: Mon Jul 18, 2005 12:55 pm
Posts: 8 Hi IR! I appreciate your help!I want to change
the manufacturer of my transitors but I can not find another PA pallet
implemented with other transistor.Do you know any manufacturer that
implements pallets of powers of 50Wrms or 100Wrms but without Freescale
transitors? Top IR Post subject: Posted: Mon
Oct 08, 2007 6:16 am Site Admin Joined: Mon Jun 27,
2005 2:02 pm Posts: 373 Location: Germany I think that NXP
do that. I will also check other manufacturers for you. Unforutnately,
I am already long time out of the PA arena. Top Corvus
Post subject: Posted: Mon Oct 08, 2007 11:30 am Captain
Joined: Mon Jul 18, 2005 12:55 pm Posts: 8 Hi again,
Anybody knows how to avoid or short circuit the diode protection
in the MRF transistor? Is it possible? thanks Top
IR Post subject: Posted: Mon Oct 08, 2007 1:51 pm
Site Admin Joined: Mon Jun 27, 2005 2:02 pm Posts:
373 Location: Germany As far as I know, the only way is to provide
the required input power so that the diode will not go into operation.
Once the diode is clamped it is too late. Look in the device
data sheet what is the allowed input power level and don't go over it.
I hope this helps.
Posted 11/12/2012
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