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Old September 9th 05, 04:13 PM
Cecil Moore
 
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Default Efficiency of Power Amplifiers

The latest QEX has an article by k9la: "The Impact of Load SWR
on the Efficiency of Power Amplifiers". The amplifier is designed
to drive a 50 ohm load and simulated measurements were made for
8 reflection coefficients of 0.333 with phase angles in 45 degree
increments.

One thing I don't understand. When driving a 100 ohm load, the
drain current is 33 amps and the efficiency is 62%. When driving
a 25 ohm load, the drain current is 12 amps and the efficiency
is 83%.

The amp is a Class E/F design from Jan/Feb 2004 QEX. Why would
the drain current fall when the load is decreased from 100 ohms
to 25 ohms?
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73, Cecil, http://www.qsl.net/w5dxp


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