ST MOSFET-Power Amplifier use???

[AndrewT]

Hi,
1pair of 200W devices can manage about 120W into 4ohm at a phase angle of 60degrees and Tc<50degC.
But into 2ohm can only increase to about 150W and at a phase angle of 42degrees, so this is your limit.

To achieve these powers the voltage amplifier will need extra PSU voltage above the +-42Vdc you are planning.

 

[quasi]

Package is TO-247, the 200Watt version of this MOSFET

As, also, I wrote in my post with short DATA for this device
in my post above
the thermal cooling factor is 0.75 C/W
and the Ciss is 4000-5000pF, which certainly is worth to consider!

Hmm...Ciss is high indeed. Zox2003 if you are going to use my cct then you should increase the drive current for the final stage. You can do this by lowering the value of R22 & R20 to 150 ohms. This lowers the impedance and will better manage the FETs combined Ciss. Note only for 40 - 50 volt rails.

Cheers

 

[zox2003]

Can you guys post any schematic??/

Thanks

 

[AndrewT]

Have you bothered to follow the links in post12?

 

[quasi]

The schematic I am refering to is here: http://www.diyaudio.com/forums/showthread.php?postid=1008216#post1008216
For rails under 50 volts R6 should be replaced with a link.

Q

 

[lineup]

Have you bothered to follow the links in post12?

that is what i wonder, too

quasi
in a post here above
does refer to some of his circuits, which could be used if you change some resistors
to possibly be able to drive those transistors of yours

---------------------------------------

Anyway
here is the latest version of a powerful quasi N-Channel design

PDF schematic attachment in Post #1123:
http://www.diyaudio.com/forums/attachment.php?s=&postid=1008216&stamp=1158583789

Post #1123:
http://www.diyaudio.com/forums/showthread.php?postid=1008216#post1008216
Topic:
Power amp under development


lineup

 

[zox2003]

OK,now I have direct question:

How much power I would be able to get from Citation 12 with one pair of output transistors?Is that acceptable schematic or ...?

 

[djk]

"How much power I would be able to get from Citation 12 with one pair of output transistors?Is that acceptable schematic or ...?"

Depends on how 'stiff' the supply is. Probably about 50W/8R with a typical ±42V supply, maybe 100W/4R with a stiff (overbuilt) one.

 

[AndrewT]

How long will 1pair last, trying to drive a reactive 4ohm load?

 

[richie00boy]

Surprisingly, possibly quite a long time if appropriate heatsink is used. I worked for a company making high quality pro audio gear, and we used a single pair for our 125W/4R MOSFET amp. They were only rated at 125W whereas these are rated at 200W. I've not compared the SOA graphs for each but I'd expect them to be similar.

We did have VI limiting which no doubt helped save these amps from destruction, but it just goes to show.

 

[lineup]

We did have VI limiting which no doubt helped save these amps from destruction, but it just goes to show.

And a BIGGER heatsink will also be important!

Two pairs= 4,
and each transistor takes 25% of the cooling power.
One pair = 2,
and each transistor will have remove twice as much heat per transistor
at equal output power level.

4 transistors will have lower thermal resistance, than only 2.
This is how many degrees the transistor inside temperature will increase per Watt.
Measured in C/W, degrees C per Watt.

 

[richie00boy]

We also did a 2x500W into 4 ohms amp, using 4 pairs per channel. However it was much bigger and heavier than what seems to be on the market these days claiming 1kW. We had big heatsinks and fan cooling.