>Regarding the SS amps question, I am a bit surprised Jon didn't jump in.
I didn't see the question posted...So I don't know what it was! :-)
And perhaps I didn't have an answer or comment (it does happen
sometimes!).
>
>Typical television transposer devices can have a gain of 30dB at UHF,
>but we used feedback to drop the gain to 10dB. Also, the transistors we
>used at 800 MHz typically had ft of 6 - 8 GHz. The result of these
>choices was a push-pull 50 watt class AB stage with 3rd order IMD of
>-60dBc.
>
>In FET amplifiers, you usually don't get the choice of using a FET
>capable of higher frequency operation - power FETs above 225 MHz are
>very hard to find.
Ok Arlen, I am confused here. You say that power FETs above 225 MHz are
hard to find. So was the device that you used that had gain up to 6 to 8
GHz a bipolar transistor? As of a couple years ago (when I left amp
design engineering) we were pushing the limit with bipolars at 1.5 GHz.
Everything that has power that I have seen at higher frequencies are
FETs. Yes, you can't use silicon typically, you have to go to Gallium
Arsenide. If you really want power up high, you have to go to a klystron
or TWT.
I was on the design team for a 3 watt or so 6 GHz amplifier. All the
devices were GaAs FETs. The power may have been more or less but it was
still a good bit of power up there.
Today the popular device is Laterally Diffused MOS FETS (LDMOS). I
really know very little about them since when I left the design world
they were just becomming popular.
Help me to understand the devices you were using.
73,
Jon
KE9NA
-------------------------------------
Jon Ogden
KE9NA
http://www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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