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Old March 3rd 05, 08:53 PM
John Woodgate
 
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I read in sci.electronics.design that gwhite wrote
(in ) about '1/4 vs 1/2 wavelength
antenna', on Thu, 3 Mar 2005:
By definition, conj-match insists RL = Ri = 110 ohms. Again we are
limited in our clipping constraint by static drain current, and supply
voltage, specifically 10 V.

Our negative swing limit is, as ever, 10 V (the drain voltage).

positive swing = Id*rL = 1*55 = 55 V

This would breakdown the device, but the lower negative swing will force
us to back down the drive to meet the design defined clipping
constraint.

Pload = 10^2/(2*110) = 0.455 W


And the power dissipated in the device is also 0.445 W. Matching
according to the 'maximum power theorem' or conjugate matching, results
in equal power in the PA and load. That's why it isn't useful for power
amplifiers.

Doesn't everyone know that an audio amplifier that id designed to feed
an 8 ohm load MUST have an output source impedance of 0.0000001 ohms or
less. An output source impedance of 8 ohms would dramatically decrease
the electromagnetic damping on the loudspeaker voice-coil - by the huge
factor of .... two!(;-)
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
 
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