Lateral MOSFET, How do I calculate power output - diyAudio
 Lateral MOSFET, How do I calculate power output
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 16th December 2007, 07:55 AM #1 diyAudio Member   Join Date: Oct 2007 Lateral MOSFET, How do I calculate power output Hello's Wondering if I can gain some insight on either rules of thumb calculations or if there are some pretty straight forward ways of calculating the power output of Lateral MOSFET based amplifiers. I realize that there are different losses at different load impedances. Typically it is assumed that the power output can be doubled by simply halving the load impedance. This is untrue however, no? I guess my question is.. Based on transformer secondary voltage, what kind of power should I expect to see in the real world at either 8,4 or 2 Ohm? Are these powers affected by more or less paralleled output devices? Typically, is efficiency lost with more output parallels? Appreciate any clarification Scott
 17th December 2007, 11:43 PM #3 diyAudio Member     Join Date: Dec 2006 also, you have a higher bias voltage for MOSFETS, which means your drivers have to swing another 3-10V for full output close to rail-to-rail. this means you actually need a higher rail voltage for at least the VAS and driver stage, so for 100W output, you will want at least +/- 70v for the VAS/drivers. to simplify things, you can make this your output rail voltage as well, but your transistors need to be 150V devices. __________________ Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net spammer trap: spammers must die
 17th December 2007, 11:55 PM #4 diyAudio Member     Join Date: Jan 2006 Location: Western Australia I go through a bit of a calculation on the webpage describing my lateral MOSFET amp, at http://www.littlefishbicycles.com/poweramp/index.html. I derived a simple formula to give Rth(max) for the heatsink, but you can easily solve for power, given Rth etc. To get the dissipated power, I found the easiest way was just to use LTspice. I designed the amp with LTspice, and simply measured the power dissipation in the output transistors.
 18th December 2007, 06:54 AM #5 diyAudio Member   Join Date: Oct 2007 Very nice! Thank You The designs I use are based on Randy Slone's work. I will be using the same Hitachi output devices. I see you are in the process of making an anti-thump circuit. Have you considered a circuit that controls the mains power based on an input signals presence? THX again

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