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On Fri, 29 Sep 2006 06:30:53 -0700, Frank Gilliland
wrote in : On 29 Sep 2006 05:40:05 -0700, "Telstar Electronics" wrote in . com: U-Know-Who wrote: 516 watts PEP, huh? You are ignorant. http://www.telstar-electronics.com/SkyWave%202879AB.pdf Actually it will do that... and more, if you will accept compression distortion. I suggest you great electronics wizards go to http://www.rf-amplifiers.com/index.php?topic=peak_power and read the defibition of PEP. Or maybe you think the people at EMPower don't know what they're talking about either... LOL Yep, their 'defibition' is right on the money. Now I suggest -you- do a little math with power dissipation and efficiency ratings. snip Since you don't want to do the math yourself, I'll do it for you..... You claim 516 watts PEP and 55% efficiency. And I'll be super-nice and say that's at 14 volts and you aren't going into saturation. So that means: 516 watts / 14 volts = 36.86 amps 36.86 amps / 55% efficiency = 67 amps 67 amps / 2 transistors = 33.5 amps Ic on each transistor. Well that's a problem since the transistor is rated for an absolute maximum of 25 amps at the collector. A paradox to be sure. But wait... An efficiency of 55% means that 45% is dissipated as heat. So: 33.5 amps * 45% = 15.1 amps 15.1 amps * 14 volts = 211 watts Wheee, that's friggin' hot!!! Especially when the device is only rated for 250 watts dissipation max, assuming a perfect heat sink! Now a 200 watt soldering gun will glow red in just a few seconds..... should we take a brief sojourn into reality and calculate junction temperature? I'm betting it will greatly exceed the max rated 175 degrees. Care to take that bet, Brian? |
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