In a message dated 2/29/2008 10:14:29 A.M. Eastern Standard Time,
wlfuqu00@uky.edu writes:
Class E amplifiers have high efficiency but what about gain and drive
power. Some that I have see have about 10db gain but unlike tube type
Grounded Grid amplifiers
I don't think any of the input power goes to the output. If so this would
reduce the overall efficiency of a single stage amplifier and driver if
the driver is not Class-E.
73
Bill wa4lav
Hi Bill,
A Class E amplifier only requires enough driving power to switch the Mosfet
Gates on and off. The Gates are capacitive so it does require some energy to
switch them on and off but for a Kilowatt-Class amplifier the driving power
would only be a couple of watts. The driving power goes up as you go up in
frequency since you are switching the capacitive gates on and off faster at
higher frequencies so it may only need a watt or two of driving power at 160
meters but perhaps 10-15 watts driving power at 10 meters.
Driving power depends on how much capacity the gates have so most people try
to choose low-capacitance-gate Mosfets for their Class-E amplifiers. There
are other factors involved depending on the Mosfet characteristics but the
gates are basically capacitive.
73 Todd WD4NGG
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