150W MOSFET Amplifier with IRFP250x2

apexaudio · 14th March 2010, 11:14 AM

This circuit is upgrade on BUZAMP from Elektor. Use only N-mosfets, with +/-50V DC give 150W on 4R load.

latala · 14th March 2010, 11:22 AM

I am interested in your amplifier can you please give furthere details
regards Trev

wahab · 14th March 2010, 11:33 AM

BC550C have a too low VCE of 45V for the +-50V rails..
Use BC546B, they have a 65V VCE..

apexaudio · 14th March 2010, 11:45 AM

Thanks Wahab. I not made this amplifier since 1995. 2SC2240, 2N5551... also can be used.

russel · 14th March 2010, 01:14 PM

Quote:

Originally Posted by apexaudio

This circuit is upgrade on BUZAMP from Elektor. Use only N-mosfets, with +/-50V DC give 150W on 4R load.

I think you may hit thermal stability problems. Use a compound mosfet and mount the drivers in thermal contact with the Vbe multiplier that sets the bias current.

apexaudio · 14th March 2010, 01:21 PM

BD139 is on heatsink with output fets for termal compenzation.

apexaudio · 14th March 2010, 02:29 PM

This two old modules (about 20 years) same circuit without curent limit, with BF422/BF433 and BUZ21x4 stil in use work on +/- 36 DC.

russel · 14th March 2010, 02:35 PM

Quote:

Originally Posted by apexaudio

BD139 is on heatsink with output fets for termal compenzation.

What bias current do you use?

apexaudio · 14th March 2010, 02:37 PM

Quote:

Originally Posted by russel

What bias current do you use?

50mA

russel · 14th March 2010, 03:00 PM

OK, thats quite low for a FET. Lateral FETS usually need 150mA and Vertical FETS are run at 400mA. If you look at the transfer characteristics in fig 3 on the link: http://www.datasheetcatalog.org/data...rf/irfp250.pdf

You can see if you ran it at 400mA there is chance of thermal runaway.

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14th March 2010, 11:22 AM	#2
latala diyAudio Member Join Date: Feb 2006 Location: staffordshire	I am interested in your amplifier can you please give furthere details regards Trev

14th March 2010, 11:33 AM	#3
wahab diyAudio Member Join Date: Nov 2009 Location: algeria/france	BC550C have a too low VCE of 45V for the +-50V rails.. Use BC546B, they have a 65V VCE..

14th March 2010, 11:45 AM	#4
apexaudio diyAudio Member Join Date: Feb 2010 Location: Serbia	Thanks Wahab. I not made this amplifier since 1995. 2SC2240, 2N5551... also can be used.

14th March 2010, 01:21 PM	#6
apexaudio diyAudio Member Join Date: Feb 2010 Location: Serbia	BD139 is on heatsink with output fets for termal compenzation.

14th March 2010, 03:00 PM	#10
russel diyAudio Member Join Date: Oct 2005	OK, thats quite low for a FET. Lateral FETS usually need 150mA and Vertical FETS are run at 400mA. If you look at the transfer characteristics in fig 3 on the link: http://www.datasheetcatalog.org/data...rf/irfp250.pdf You can see if you ran it at 400mA there is chance of thermal runaway.