----- Original Message -----
From: John Lyles <jtml@lanl.gov>
To: <amps@contesting.com>
Sent: 06 December 2002 20:41
Subject: [Amps] RF103 info received! MOSFET Question
> I will pose a work-related technical question for the solid state RF
> power experts. What is the biggest or highest power MOSFET device I
> can get for linear (AB) operation at 200 MHz? Am already using a
> crate full of parallel and combined MRF151G devices to get 5500 Watts
> pulsed. I see that PolyFet has devices, M/ACOM (Tyco!) has the MRF
> line, possibly Ericcson (sold off?), ST Electronics, Semelab.
> Others? Seems that the practical limit for Standard V or D MOS is
> about 400-500 watt dissipation devices. The HOGFET (MRF154) wasn't
> rated above 100 MHz, and thats pushing it. LDMOS isn't really pushed
> for VHF range, and I would rather stick with MOSFETs. Most solid
> state TV transmitters seem to use the 151G, and the MRI/NMR
> amplifiers may also. I look forward to hearing some good discussion.
> (fyi, I need 16 kW peak at 200 MHz, with 15% duty factor pulsed to
> drive a tube).
>
You might find Semelab D1029 worth looking at. It's up over 300W cw at
225MHz, it was developed for the 220MHz Digital Audio transmitters in
Europe. Depending on your pulse length, you might be able to run a little
more. The datasheet curves run up to 400W out with remarkable efficiency.
The efficiency appears to be a bit of a fluke in the test fixture, probably
tied up with harmonic load lines. The big advantage over 151G will be the
gain - I think they can supply a guaranteed 17dB+ at 300W out and probably
select for more, so the driver stages get smaller.
Steve
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