[Amps] High voltage MOSFETs

[Jim Thomson]

Date: Wed, 3 May 2017 23:09:35 +0100
From: Steve Thompson <g8gsq72 at gmail.com>
To: amps at contesting.com
Subject: Re: [Amps] High voltage MOSFETs


>I think most of these are products inherited when they took over 
>APT. There's a number of app notes to go with them - they were 
>originally designed for narrow band saturated cw use and one 
>common theme is the problems of trying to use them as linear amps. 
>Bias control is a problem and reduced supply voltage is 
>recommended, even then linearity is poor. One 'linear' design 
>quotes IMD as -25dB ref pep or -19dBc!

>I dare say they are capable of better than that, but it won't be 
>simple and straightforward.

>Steve

##  Well at least its better IMD than the 400w yaesu  9000MP. 

##  ISM usage is one thing, or other single freq, single band applications,
or non linear, low duty cycle, pulsed modes.

##  for amateur use, we are still stuck with barely 50%  eff, and lousy imd.
Drop the po in half,  imd improves, but eff drops to  35%. 

##  perhaps whats needed is to focus on the xcvr, and get the imd way down,
po way up, and improved cooling techniques for high duty cycle modes. 
Then leave the real job of generating loads of power to tubes. 

Jim  VE7RF