HEXFET amp - please help me fix it. - Page 2

EDDELARUE · 12th February 2009, 09:15 PM

Oh ! I forgot to say....
The numbers of components are diferent from original Elektor article - September/1995 issue - but not the circuit. In orange color there are the modifications from Elektor - April/2001-pg.58 "Crescendo Millenium Edition" issue. Not valid to R20 and R21 on "my" circuit because it not uses IGBT as output transistors.

meanman1964 · 13th February 2009, 05:46 AM

Hi Eddelarue,

As I can see you are using the schematic of the IGBT amp and not from the Hexfet amp am I right?

EDDELARUE · 13th February 2009, 10:10 AM

Quote:

Originally posted by meanman1964
Hi Eddelarue,

As I can see you are using the schematic of the IGBT amp and not from the Hexfet amp am I right?

Hi meanman1964 ,

Yes, you are rigth.

This configuration works very well too.

meanman1964 · 13th February 2009, 10:18 AM

Is the output wattage the same as the IGBT?The IGBT has 90Watts how much is your version?

Patrick

EDDELARUE · 13th February 2009, 11:02 AM

Quote:

Originally posted by meanman1964
Is the output wattage the same as the IGBT?The IGBT has 90Watts how much is your version?

Patrick

This version is the same as the original Elektor - september/1995 issue. I just modified the output transistors. I use power mosfets - IRFP240 and IRFP9240. For this application, they differ from original IGBTs basically on maximum drain current of Pchannel device (GT20D201=20A and IRFP9240=12A ) and the maximum power dissipation (GTs=200W and IRFs=150W ). I believe that IRFs works as the same in this amplifier as IGBTs works without losses. If you want, you may use two pairs os this mosfets in paralleled mode. I didn´t this yet.

meanman1964 · 13th February 2009, 11:26 AM

Did you make your own PCB and can you make a layout of this board for two output pairs?

EDDELARUE · 13th February 2009, 12:22 PM

Quote:

Originally posted by meanman1964
Did you make your own PCB and can you make a layout of this board for two output pairs?

No. Some years ago I made the pcb from original article ( that uses IGBT ). Do you have it ?

meanman1964 · 13th February 2009, 01:05 PM

I do have the original layout on Elector cd but never made PCB's myself maybe there is someone who can redraw the layout for use of two pair of output fets

Beto · 14th February 2009, 07:33 PM

this scheme does not need the Zener diode to protect the gate of the fet?

how this protection to avoid damaging the gate of the fet ?.

raise0 · 14th February 2009, 08:13 PM

Quote:

Originally posted by meanman1964
Did you use the IRFP240 and IRFP9140 fets aswell?

Well i only did the changes i mentioned. I use the original hexfets. It works just fine, with no problems, for almost a year now. If you get the parts right it has no reason to oscillate.

Interesting mods EDDELARUE. Although i prefer to stick with the original design using IRF540 and IRF9540. I cannot afford to upgrade my PSU.

Quote:

Originally posted by Beto
this scheme does not need the Zener diode to protect the gate of the fet?
how this protection to avoid damaging the gate of the fet ?.

I don't think that a Zener diode is necessary. I'm afraid that it may degrade sound quality, but I'm not sure.

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13th February 2009, 05:46 AM	#12
meanman1964 diyAudio Member Join Date: Oct 2006 Location: Belgium the land of chocolate	Hi Eddelarue, As I can see you are using the schematic of the IGBT amp and not from the Hexfet amp am I right?

13th February 2009, 10:18 AM	#14
meanman1964 diyAudio Member Join Date: Oct 2006 Location: Belgium the land of chocolate	Is the output wattage the same as the IGBT?The IGBT has 90Watts how much is your version? Patrick

13th February 2009, 11:26 AM	#16
meanman1964 diyAudio Member Join Date: Oct 2006 Location: Belgium the land of chocolate	Did you make your own PCB and can you make a layout of this board for two output pairs?

13th February 2009, 01:05 PM	#18
meanman1964 diyAudio Member Join Date: Oct 2006 Location: Belgium the land of chocolate	I do have the original layout on Elector cd but never made PCB's myself maybe there is someone who can redraw the layout for use of two pair of output fets

14th February 2009, 07:33 PM	#19
Beto diyAudio Member Join Date: Feb 2008	this scheme does not need the Zener diode to protect the gate of the fet? how this protection to avoid damaging the gate of the fet ?.