Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
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My Hobby Website:
Freescale MRF transistor - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
platforms dominating public commenting venues. RF Cafe Forums began sometime around
August of 2003 and was quite well-attended for many years. By 2010, Facebook and
Twitter were overwhelmingly dominating online personal interaction, and RF Cafe
Forums activity dropped off precipitously. If the folks at
phpBB would release a version with integrated
sign-in from the major social media platforms, I would resurrect the RF Cafe Forums,
but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
-- CAE, CAD, &
Test & Measurement
Post subject: Freescale MRF transistor Posted: Fri Oct 05,
2007 9:19 am
Joined: Mon Jul 18, 2005 12:55
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?
Post subject: Posted: Fri Oct
05, 2007 3:04 pm
Joined: Mon Jun 27, 2005
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....
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.
Post subject: Posted: Mon Oct 08, 2007
Joined: Mon Jul 18, 2005 12:55 pm
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
Post subject: Posted: Mon
Oct 08, 2007 6:16 am
Joined: Mon Jun 27,
2005 2:02 pm
I think that NXP
I will also check other manufacturers for you. Unforutnately,
I am already long time out of the PA arena.
Post subject: Posted: Mon Oct 08, 2007 11:30 am
Joined: Mon Jul 18, 2005 12:55 pm
Anybody knows how to avoid or short circuit the diode protection
in the MRF transistor? Is it possible?
Post subject: Posted: Mon Oct 08, 2007 1:51 pm
Joined: Mon Jun 27, 2005 2:02 pm
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.