A power amplifier can be reduced to the Thevenin
equivalent circuit of a voltage source with a
series resistor source impedance. Power transfer
is maximized when the load impedance is equal to the
source impedance.
Simple example:
12 volt source with 4 ohm source impedance.
If the load impedance is 2 ohms, 2 amps flows and the power
to the load is 8 watts.
If the load impedance is 4 ohms, 1.5 amps flows and the
power to the load is 9 watts.
If the load impedance is 8 ohms, 1 amp flows, and the power
to the load is 8 watts.
Dave Hachadorian, K6LL
k6ll@juno.com
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