my new ampli mosfet

xcicc · 5th August 2008, 12:53 PM

Hi, I try to make this ampli any suggestion?
regard
A.

darkfenriz · 5th August 2008, 01:25 PM

Check out current sources and polarity of P-fet.

xcicc · 5th August 2008, 03:07 PM

Quote:

Originally posted by darkfenriz
Check out current sources and polarity of P-fet.

Hi made some change the polarity on P-fet and I add the voltage...
A.

richie00boy · 5th August 2008, 03:35 PM

I think the output bias scheme will give you problems due to wide tolerance of Vgs. Also I think there is massively insufficient drive to the output MOSFETs.

fab · 5th August 2008, 03:43 PM

Hi,

Is there a triac between the amp output and input of drive of mosfet2? if so, what is its purpose. Is it a protection and how is it suppose to work?

Thanks

xcicc · 5th August 2008, 08:30 PM

Quote:

Originally posted by fab
Hi,

Is there a triac between the amp output and input of drive of mosfet2? if so, what is its purpose. Is it a protection and how is it suppose to work?

Thanks

Hi, yes the purpose of this triac is for short circuit protection.
why? is useless??
A.

Wavebourn · 5th August 2008, 08:44 PM

You are still forgetting about powering of left upper current sources.

fab · 6th August 2008, 02:11 AM

Quote:

Originally posted by Wavebourn
You are still forgetting about powering of left upper current sources.

He's right. At least a resistor should be put from the diodes-transistors base connection point to either ground or negative power rail.

xcicc · 6th August 2008, 05:36 AM

Quote:

Originally posted by fab

He's right. At least a resistor should be put from the diodes-transistors base connection point to either ground or negative power rail.

Hi, you mind this? I made some correction I hope is right...

lineup · 6th August 2008, 05:56 AM

Latest attachment.
http://www.diyaudio.com/forums/attac...amp=1218000976

It might work.
But personally I woul use a little bit more current to bias the GATES of IRFP140/9140

28Volt/100kohm ~ 0.3 mA
Make those 100 kohm resistors ~27 kohm .. or even 10 kohm
Would give: ~ 1 - 3 mA

Also I would connect those bias resistors ( 100kohm / 27 kohm )
BEFORE those gate stoppers ( 47 Ohm resistors ).

If you change from 100 kohm .. to 27 kohm,

then you should make those 47 kohm (in parallel with 4.7uF) smaller, too.
Maybe like 4k7.
And those two (now 47 kohm) should be connected to GROUND.
To try and keep, hold, the output MOSFETs at zero DC Offset.
The point between those two resistors, I mean, should be connected to GND.

5th August 2008, 03:35 PM	#4
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	I think the output bias scheme will give you problems due to wide tolerance of Vgs. Also I think there is massively insufficient drive to the output MOSFETs. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

5th August 2008, 03:43 PM	#5
fab diyAudio Member Join Date: Mar 2004 Location: Canada	triac? Hi, Is there a triac between the amp output and input of drive of mosfet2? if so, what is its purpose. Is it a protection and how is it suppose to work? Thanks

5th August 2008, 08:44 PM	#7
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	You are still forgetting about powering of left upper current sources. __________________ The devil is not so terrible as his mathematical model! Wavebourn: We Create Creativity!

6th August 2008, 05:56 AM	#10
lineup diyAudio Member Join Date: Dec 2005 Location: the north	Latest attachment. http://www.diyaudio.com/forums/attac...amp=1218000976 It might work. But personally I woul use a little bit more current to bias the GATES of IRFP140/9140 28Volt/100kohm ~ 0.3 mA Make those 100 kohm resistors ~27 kohm .. or even 10 kohm Would give: ~ 1 - 3 mA Also I would connect those bias resistors ( 100kohm / 27 kohm ) BEFORE those gate stoppers ( 47 Ohm resistors ). If you change from 100 kohm .. to 27 kohm, then you should make those 47 kohm (in parallel with 4.7uF) smaller, too. Maybe like 4k7. And those two (now 47 kohm) should be connected to GROUND. To try and keep, hold, the output MOSFETs at zero DC Offset. The point between those two resistors, I mean, should be connected to GND. __________________ lineup

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5th August 2008, 01:25 PM	#2
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	Check out current sources and polarity of P-fet.

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