[Amps] Class-E Amplifiers

[ToddRoberts2001 at aol.com]

In a message dated 2/29/2008 3:04:05 P.M.  Eastern Standard Time, 
wlfuqu00 at uky.edu writes:
You can't simply
tune out  the capacitance with inductance and say you have no power loss
on the input  of the device.  5 or 10 percent drive power compared the output
lowers  the overall efficiency by another 5 or 10 percent.
That 85 to 90 percent  efficiency could just as well be 75 to 80 percent.
More like a class-C tube  amplifier.

73
Bill wa4lav  


Hi Bill,
        There is some non-linearity to  the capacitance of the Mosfet when 
driving the gate due to Miller effect. The  peak driving power may be 20-30 
watts  but the average driving power may be  only 5 watts or less for a kilowatt 
Class-E amp on 160 meters. 5 watts driving  power is 1/2 of 1 percent drive 
power for a kilowatt-input Class-E amplifier.  How does that lower efficiency by 
up to 20%?
 
73 Todd WD4NGG



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