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what is Vref+ and Vref- in the sch above...
I believe IN+ and IN- from the VAS stage but the amplifier symbol in between ( triangle ) why is that for?
Im planning to use these with LME49830 as VAS and the ckt intended to be used either with IRF hexfet or Exicon
since lme series cant be used beyond 80-90V 100 being limit is there anyway that we can split these into tier like for the output since the output voltage is being shared by 4 output devices ( two for positive wave and two for negative ) now Im thinking to use two lme49830 one for positive and one for negative wave so finally is it possible to use lme chips in the above case?
The voltage at which you want the upper device to turn on. Normally a few volts below VL+ (on the upper half). The "triangle" is the notational symbol for a comparator. When IN+ exceeds Vref+, the upper hexfet turns on and then the output stage runs off VH+. This is a very oversimplified conceptual schematic, far from a working output stage. Getting the bias into the comparators usually involves bootstrapping a floating power suppy to them - and keeping the comparator inputs within the common mode range so you don't fry them. There are several topologies that work, I suggest studying the QSC circuits or the Apex 900W circuit posted in this forum.
To use this with a normal amp front end topology, the VAS must be able to operate off the full VH+/VH- supply. To try to split it up where one chip amp does the + half and one the - half is probably asking for crossover distortion if not other severe problems. It may be possible to boot strap the supply for an LME front end so that it never sees more than rated Vcc. A long time ago there was a schematic for running an entire power op amp (LM12?) in class H at high voltage with external transistors. You might be able to find that and do a similar concept. In any case, you've got a LOT of homework to do.
To use this with a normal amp front end topology, the VAS must be able to operate off the full VH+/VH- supply. To try to split it up where one chip amp does the + half and one the - half is probably asking for crossover distortion if not other severe problems. It may be possible to boot strap the supply for an LME front end so that it never sees more than rated Vcc. A long time ago there was a schematic for running an entire power op amp (LM12?) in class H at high voltage with external transistors. You might be able to find that and do a similar concept. In any case, you've got a LOT of homework to do.
http://www.peaveycommercialaudio.com/media/schematics/9001_schematic_set1.pdf
Also see page 8 here:
http://www.peaveycommercialaudio.com/media/schematics/vvs_schematic_set1.pdf
You will probably not need multiple parallel devices for the top rails (unless you are making a multi-kilowatt amplifier as shown in the schematics). Fairchild has some big P-channel FETs that would work.
http://www.digikey.com/product-detail/en/FQA36P15/FQA36P15-ND/1057384
Also see page 8 here:
http://www.peaveycommercialaudio.com/media/schematics/vvs_schematic_set1.pdf
You will probably not need multiple parallel devices for the top rails (unless you are making a multi-kilowatt amplifier as shown in the schematics). Fairchild has some big P-channel FETs that would work.
http://www.digikey.com/product-detail/en/FQA36P15/FQA36P15-ND/1057384
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Those Crests are back from the day when Rds(on) was a factor of 10 higher than it is today. A single 200A FET is enough, even for an amp that big. And they're about $7. A single cheapo IRF1407 is good enough for rails under 120V.
Design the comparators right, and you can use N channel on both rails.
Design the comparators right, and you can use N channel on both rails.
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