Can you suggest a schematic were i can use this FET into the output?

I have many of them.... looks huge ones.

Please, post the schematic that will work fine with those ones.

Here is the Data sheet.




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Was a gift from a forum friend, Dudainc... and now i want to put those ones to play

I have many... would like to use them into output, having transistors into the other stages.

Yes, quasi complementary may fit my needs.

I can try to create the circuit...but why to take those risks when we have, in our forum, hundreds of skilled folks to operate with Fets (I am not skilled with them).... so.... already tested schematic will be excelent.




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Yeah...i can install a zener and diodes and produce 4 volts to it.

But this is not the entire knowledge about Fets.... skilled guys have things to say, advises to give.

It is different when guys are skilled.... i am new into Fet.

All i know they have gate, drain and source and works sligtlhy different..have capacitance into the input.... charge and do not conduct input DC current..only AC current into the input... strange folks...and we need bigger bias voltage to force them to operate.... very strange folks those Fets!

Negative!..please, not those fanatics by fets with amplifiers using fet!!!.... only the output friends, please!




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Paid Member
2007-07-17 2:35 am
Central Berlin, Germany
Hi Carlos,

maybe something like this, preferably a class-A variant and in bridge mode (because of the low Vds)?

This MOSFET has really a lot of capacitance and needs a hard drive... and maybe it is quite non-linear at reasonable currents (note that the curves start in the 10A region) -- there are chances it will not be good for audio. But one would certainly need to try it, so go ahead...

I once used a somewhat similar monster, the IRFP2907, in a power supply (as a cap multiplier), where it perfomed well. No audio application, though.

Regards, Klaus
Hi Carlos,

my O/S configuration would work well with these devices. You can build a single 50V supply bridge amp, capable of 100W into 8 Ohm, 200W into 4 and happily delivering 400W into 2 Ohm load. If you only need it for a subwoofer, than it can be quite simple as you don't need a lot of speed. However it is also possible to build a good full-range amp with these devices. A simplified circuit I've simulated using somewhat similar size FETs (IRF1405) for the output, set for 600mA idle (15W dissipation on each transistor) shows about 0.07% THD at 1 kHz, 40V p-p into 4 Ohm and 0.1% into 2 Ohm.




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Thank you Todd.... i have constructed quasi amplifiers..he is a good friend

and an excelent designer.

I would like to produce some different know.... we love new things, different ideas, sligthly different schematics, to listen, to evaluate, to understand more, to learn more.

New ones are more pleasant than build, once again, some of Quasi amplifiers.... i made many amplifier from Quasi

I will build this one RAJ have just sent me.




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> we love new things, different ideas, ....
> i made many amplifier from Quasi
> I will build this one RAJ have just sent me.

Is that not also a quasi, a la Linsley Hoood Class A with the phase splitter ?

If you really want to build something different, try a circlotron.
Done it twice, love it to bits .....


Here you have the board

I have not parts list for this one...if you are interested, search for RAJ into the forum and ask him by the part's list.

Raj will go to travel to Singapore today.... so...needing to find him, wait a couple of days when he wil be back home.

I will build the old version.... if approved, then i will update it




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Can you provide me a link to some free to use schematic from Pass?

I had not Fets easier here...also i have visited Nelson Pass forum section, years ago, and could not find free schematic (those two days i have visited)...than i give up to read pass section...i concluded not for me ..because i was searching for something transistorized and free to assemble.

Are those Pass amplifiers free to use, with published schematics?

No criticising...not that way.... he can do whatever he wants...but i have perceived not for me.... i wanted for free..not to buy kits, or something...maybe i was wrong and there's a lot of free published schematics there... if really this way i will be visiting constantly his section from now on.

Can you suggest something, giving me the link to the schematic and diy instructions?

I have, now a days, something alike 100 huge FETs N and channel P...but nothing complementary.... some of them to 100 volts and 40 constant course not both same time....just maximum absolute volts and currents.


Yes..for sure he is..but, because difficult to find here, Fets are not "my beach"

And he use Fets all time my beach there.

Now i have fets, so... i may be able to construct some of his amplifiers....not many, i do not like class A amplifiers because of environment is too much hot for is silly to use those heaters is already a hell hot here!

Or i install the amplifier out from my home or i have to listen the music outside my home..but environment heaters and Brazilian Northeastern weather do not combine.

Even knowing they sound great (class A)...i think they can overheat other place than my place.... no problems with Pass..problems with class A and Fets only.