I acquired a commercial power amplifier at Dayton, and I'd like to use it on
6. It's obviously biased for Class C right now, however. Looking in my data
books, nowhere is there a procedure given for properly biasing an amplifier to
Class AB.
The amp has 8 MOSFETs, each with their own bias pot. But I don't have
individual current metering for each device, obviously. My thought is to
bias each device to cutoff, measure the remaining current draw, then one at a
time set the bias pots to draw some amount of current. Is there another way to
properly bias a multi-stage amplifier like this?
Second question. To what value should I set the quiescent drain current to put
the device (MRF150) in the linear region? If the maximum rating is 16A, do I
set it for 1/10 of that? Is there a rule of thumb for this? The common source
unity gain frequency peaks at Id of about 7.5 A, but that doesn't seem
reasonable to use.
Third, does anyone have the schematic? It contains 2 channels of 2 MRF148s
driving 2 MRF150s, and was used in a medical application to drive 3cx800s.
Thanks for any advice.
--
...Dave Phillips | Internet: phillipsd@saic.com
The *MAGIC* band: 6 meters | Amateur Radio W7GZ, grid DM42nf
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