Did someone tryed this?

MaXiZ · 21st December 2003, 10:10 AM

MaXiZ · 1st January 2004, 12:59 PM

no one tryed this?

millwood · 1st January 2004, 01:33 PM

I haven't tried it. But CFPs on MOSFETs, especially the non-lateral types, are tough to get to work. they usually break into parasitic oscillation at the smallest disturbances.

rtirion · 1st January 2004, 01:42 PM

This is de hexfet amp published some years ago in elektuur.
<B>Copyrighted material.</B> There was an update in 2001/2002 that sufficiently dealt with oscillations in some implementations.

Audiofanatic · 1st January 2004, 10:46 PM

Quote:

Originally posted by millwood
I haven't tried it. But CFPs on MOSFETs, especially the non-lateral types, are tough to get to work. they usually break into parasitic oscillation at the smallest disturbances.

Hi Millwood,

CFPs ? Can you be more specific? Thank you!

Audiofanatic

P.S. I have the PCB's

jean-paul · 1st January 2004, 11:07 PM

Complentary Feedback Pair=> a topology of 2 complementary transistors wired together a certain way.

See this thread were these things are discussed briefly:

"Super-Pair" I/V for TDA1543

sam9 · 1st January 2004, 11:12 PM

Just a suspicion, but the oscillation that Millwood mentions may be the reason for the reason for the resistors between the emmitters of the BD139/40 and the drains of the FETs. In a CF-type BJT ouptut section, the emitters of the drivers and the collectors of the output devices are directly connected. Putting resistors in between may be intended to reduce the tendency to oscillate. Just a guess.

At the same time I notice that the gate stopper resistors are only 15-ohms. These also are intended to suppress oscilation, but that looks like an awfully low value. I'm more used to seeing 400-1k ohms used for these.

The placement of the rail fuses is a bit brave, at least from the perspective of one who has found more than one way to short an amp!

What is the origin of this schematic? Was/is it a commercial product?

Audiofanatic · 1st January 2004, 11:53 PM

Quote:

Originally posted by jean-paul
Complentary Feedback Pair=> a topology of 2 complementary transistors wired together a certain way.

See this thread were these things are discussed briefly:

"Super-Pair" I/V for TDA1543

Thanks JP!

Audiofanatic

MaXiZ · 2nd January 2004, 09:31 AM

so this should work?

Vigier · 2nd January 2004, 10:03 AM

Yes,

it DOES work; I have 2 of them myself, and they work without any problems, no oscillation or whatsoever.
@rtirion: the "update" for the oscillation-problem was NOT for this amplifier, it was for the upgraded version of this amp with a pair of GT20D101/GT20D201 IGBT's.

Grtz, Joris

21st December 2003, 10:10 AM	#1
MaXiZ diyAudio Member Join Date: Jun 2003 Location: Italy	Did someone tryed this?

1st January 2004, 01:42 PM	#4
rtirion diyAudio Member Join Date: Nov 2000	Hexfet This is de hexfet amp published some years ago in elektuur. <B>Copyrighted material.</B> There was an update in 2001/2002 that sufficiently dealt with oscillations in some implementations.

1st January 2004, 11:07 PM	#6
jean-paul diyAudio Moderator Emeritus Join Date: Sep 2002 Location: The Netherlands	Complentary Feedback Pair=> a topology of 2 complementary transistors wired together a certain way. See this thread were these things are discussed briefly: "Super-Pair" I/V for TDA1543 __________________ It's only audio

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1st January 2004, 12:59 PM	#2
MaXiZ diyAudio Member Join Date: Jun 2003 Location: Italy	no one tryed this?

1st January 2004, 01:33 PM	#3
millwood Account Disabled Join Date: Apr 2003 Location: US	I haven't tried it. But CFPs on MOSFETs, especially the non-lateral types, are tough to get to work. they usually break into parasitic oscillation at the smallest disturbances.

1st January 2004, 11:12 PM	#7
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	Just a suspicion, but the oscillation that Millwood mentions may be the reason for the reason for the resistors between the emmitters of the BD139/40 and the drains of the FETs. In a CF-type BJT ouptut section, the emitters of the drivers and the collectors of the output devices are directly connected. Putting resistors in between may be intended to reduce the tendency to oscillate. Just a guess. At the same time I notice that the gate stopper resistors are only 15-ohms. These also are intended to suppress oscilation, but that looks like an awfully low value. I'm more used to seeing 400-1k ohms used for these. The placement of the rail fuses is a bit brave, at least from the perspective of one who has found more than one way to short an amp! What is the origin of this schematic? Was/is it a commercial product?

2nd January 2004, 09:31 AM	#9
MaXiZ diyAudio Member Join Date: Jun 2003 Location: Italy	so this should work?

2nd January 2004, 10:03 AM	#10
Vigier diyAudio Member Join Date: Nov 2002 Location: Netherlands	Yes, it DOES work; I have 2 of them myself, and they work without any problems, no oscillation or whatsoever. @rtirion: the "update" for the oscillation-problem was NOT for this amplifier, it was for the upgraded version of this amp with a pair of GT20D101/GT20D201 IGBT's. Grtz, Joris

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