[Amps] Freescale LDMOS devices / load mismatch survival

[George]

Leigh, the idea of having a device without external means for protection 
is intriguing.
A device that can sustain such repetitive abuse and continue to operate 
is really something.
As you said stated it could be done with standard methods, however they 
do marginal
SWR, and high current shutdown.  If you've seen the test video of the 
NXP device on Youtube,
the power output never shuts down, just simply sits in ready for the 
mismatch to clear.

73,
George, K4GVT



On 3/9/2013 9:13 PM, Leigh Turner wrote:
> I'm always intrigued and puzzled why so many hams place so much reliance on
> inherent brute force device survival per se when placing their amplifiers
> through this kind of severe load and phase angle mismatch test.
>
> With appropriate design and implementation of ancillary load impedance
> sensing, protection, and fast acting shut-down circuitry then less rugged,
> lower VDS breakdown QRO MOSFET devices will readily survive any VSWR load
> you can throw at them.  Existing MOSFET RF devices are more than capable.
>
> Inadequate thermal design issues that don't keep the actual device flange
> temperature low enough are far more likely to be the underlying cause of
> premature device failure in practical SS amplifiers.
>
> Leigh
> VK5KLT
>
>
> -----Original Message-----
> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of George
> Sent: Sunday, 10 March 2013 11:13 AM
> To: Paul Decker
> Cc: amps at contesting.com
> Subject: Re: [Amps] Freescale LDMOS devices
>
> Very nice Paul, have you put it through the ringer regarding mismatch,
> open, or short.
>
> 73,
> George, K4GVT
>
>
> On 3/9/2013 6:46 PM, Paul Decker wrote:
>
>> I don't know how the freescale parts are, but the NXP BLF578XR seems to be
>> holding up well for me.  with 4 watts I can drive it to about 1450W output
>> with 52V @ 42A.  I've been running it ~45% duty cycle 45s on 75s off with
>> wsjt on 2m without issues.
>>
>> Paul,
>> KG7HF
>>
>>
>> Date: Sat, 09 Mar 2013 09:23:52 -0500
>> From: George
>> To: jtml at vla.com
>> Cc: amps at contesting.com, John Lyles
>> Subject: Re: [Amps] Freescale LDMOS devices
>> Message-ID: <513B45F8.1090306 at comcast.net>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> John, sounds like a great commercial project with quite an end result
>> most Hams will never see.  I am very curious about your testing.
>> Be very interested if you had any fault history for the MRFE6VP61K25H.
>> Have you pushed it to extremes.
>>
>> 73,
>> George, K4GVT
>>
>> _______________________________________________
>> Amps mailing list
>> Amps at contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
>
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>