[Amps] Freescale LDMOS devices / load mismatch survival

[Peter Frenning [OZ1PIF]]

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

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