Giga Mosfet

[Tyimo]

Hi!
In the attached link you can see that the Thorens Tem 3200 use only one giga power mosfet, 800W/300A.
Could somebody tell me what is that Mosfet? What type?
Maybe it would be suitable for some Pass amp.

http://www.6moons.com/audioreviews/thorens/thorens.html

Greets:

Tyimo

[woody]

Yes those big ones seem interesting but come with some problems. They tend to be expensive an 800w device is probably
going to cost $30 or more. And the darn input capacitence
is also huge something like 12,000pf for a 800w device!
They do have the added feature of not requiring a heatsink
insulator. By the way Nelson said in his original ZEN article
that he did play with some 600w mosfets.

[RS232]

I used to use this type of mosfet in industrial electronic (phase inverters/ac speed controlers).

Ric

[EUVL]

Apart from all those disadvantages mentioned, these industrial MOSFETs do not really have high transconductance at low bias current, which is what you want really for audio.

If you want high gain (transconductance) MOSFETs, you are better off using UHC MOSFETs, e.g. 2SK2955. There are even P-devices, so you are not forced to do quasi or circlotron. AND you can still parallel them if you really want them to dissipate 800W.


Patrick

[Tyimo]

Yes those big ones seem interesting but come with some problems. They tend to be expensive an 800w device is probably going to cost $30 or more. And the darn input capacitence
is also huge something like 12,000pf for a 800w device!
They do have the added feature of not requiring a heatsink
insulator. By the way Nelson said in his original ZEN article
that he did play with some 600w mosfets.

These are not insoluble problems...

The main question is:
What is that industrial 800W/30A mosfet???? Code number??

Tyimo

[Lars Clausen]

It does say: One single 800W N-ch MOSFET per phase leg..

Which makes it a traditional push-pull amplifier anyway.

Could be this device: http://ixdev.ixys.com/DataSheet/45a8...6a6a893e15.pdf

[Tyimo]

Yes, maybe, but in the Thorens page there is 800W/300A.

Could this be a mistypeing?!?

Tyimo

[poynton]

This whole topic was discussed at length over a year ago - not on the Pass Labs section though.
A good search should find it.

Andy


edit - found it

Does someone knows what mosfet is this?

[Lars Clausen]

You can find higher current devices on IXYS.com but then with lower Voltage. It appears this way of selecting MOSFET's is based more on testosteron than common sense.
The oversized MOSFET will have too much Gate capacitance, making the closed loop slow. And the only place you dont want slowness is in the closed loop. That, combined with the unlinear low current region of any MOSFET, is what makes your amplifier sound hard and metallic.

Always select the smallest MOSFET that will do the job, for this kind of amplifier.

[Tyimo]

This whole topic was discussed at length over a year ago - not on the Pass Labs section though.

Yes, thanks, but as you see there wasn't the right answer.

Tyimo