Copper Talk » Ask The Tech » Amplifiers » Volts X Amps= Watts ???????????????????? « Previous Next »

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Hilljack_357
New member
Username: Hilljack_357

Post Number: 2
Registered: 3-2006
Posted on Monday, July 31, 2006 - 10:17 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Ok heres the question if a 2SC2879 transistor has a maximum collector current of 25 amps which voltage are you suppose too use to calculate watts?
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Kid_vicious
Senior Member
Username: Kid_vicious

Post Number: 1932
Registered: 9-2004
Posted on Monday, July 31, 2006 - 7:11 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

sorry hilljack, it doesnt quite work like that when dealing with linear amps.
the reason is because they are not 100% efficient.
each amp design will have different efficiencies, depending upon how they are built and which class they are.

the way your equation is supposed to work is like this:
if you are feeding your amp with 15 volts, and when you key the mic, it is drawing 25 amps, then the wattage out would be 375 watts.

obviously, you are not going to get this kind of wattage out of a single 2SC2879.
thats because the amp is only running at somewhere around 40-60% efficiency. thats just how they are, the rest is lost as heat.

the best way to find out what an amp "should" be doing is to search around the forum for product reviews of the particular amp.
good luck,
matt
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Hilljack_357
New member
Username: Hilljack_357

Post Number: 3
Registered: 3-2006
Posted on Tuesday, August 01, 2006 - 12:03 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Thanks for the information Kid_vicious, I've read that class AB1 is suppose to be 65 % and class C is between 75-80 %, I was just wondering how their getting the wattage they claim when the data sheets for each transistor shows maximum specifications. It just didn't add up too me.Again thanks for the info!

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