Den 11-03-2013 09:01, Steve Thompson skrev:
The video is, indeed, impressive - but it could also give a false
impression. The transistor operating spec. is 100us pulses at 20% duty
cycle - 100us on, 400us off. Looking at the current drawn during the
variable load pull test, it's not running cw. Also, the test is being
done at 200MHz and ruggedness doesn't necessarily translate to lower
frequencies for those thinking of hf applications.
At 100us long pulses, the die inside probably isn't reaching the peak
temperature for any given dissipation which makes high VSWR survival
easier.
F1JRD tested Freescale devices with all phases of high load VSWR
running 10ms pulses, low duty cycle. They survived, so a trip circuit
acting faster than that should protect them. I'd expect NXP parts to
be similar.
Steve
I, inadvertently, tested mine when the output coax relay gave up it's
ghost, see the pictures toward the bottom of the page:
http://www.frenning.dk/OZ1PIF_HOMEPAGE/LDMOS_SSPA.html
The LDMOS survived! I was running Digimode at about the 750W level when
it failed.
--
Vy 73 de OZ1PIF/5Q2M, Peter
*****************************************
** Women and cats will do as they **
** please, and men and dogs should **
** relax and get used to the idea. **
** -- Robert A. Heinlein **
*****************************************
email: peter(no-spam filler)@frenning.dk
http://www.frenning.dk/oz1pif.htm
Ph. +45 4619 3239/ +45 2332 9464
Snailmail:
Peter Frenning
Ternevej 23
DK-4130 Viby Sj.
Denmark
*****************************************
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|