High volts for high amp efficiency ? - RF Cafe Forums
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Post subject: High volts for high amp efficiency ?
Unread post Posted: Thu Feb 03, 2005 8:06 am
From say 100 MHz to 1GHz I would imagine that operating RF amplifiers with a higher supply voltage should result in higher efficiency. My reasoning is pretty simple....... Higher Volts must mean lower currents for a fixed output power, where I assume that the majority of loss is due to I squared R. Anyone care to comment?
Of course, unless you happen to get just the right impedance with the chosen rail and output power you will need to impedance match. It may be the case that a lower supply rail would mean you could do away with the match and reduce losses incurred in this part of the circuit.
We then get into greater detail with just where the transistor is operating (with regard to saturation). Not to mention those funny games you can play with harmonic terminations and switching classes such as class E but to keep the discussion simple lets ignore these for now.
In any case, even if high volts does gain you somthing the chances of building anything seem slim to me as I find that most of the new transistor stuff around is aimed at low supply rails.