Mosfet IRFP240/9240

BrianVG · 26th June 2010, 09:12 AM

Hello everyone,

I have found a low power amplifier with the IRFP240/9240.
At some fora I saw that this design has some problems like the LED and the
cermet trimmer.

Thank you.

balaboo · 26th June 2010, 02:18 PM

Despite what you have heard, the design will work just fine - make sure the bias current is between 20ma-50ma, and use a nice thick heatsink. I have a similar design as a guitar amplifier that is run at full blast with no thermal runaway issues.

AndrewT · 26th June 2010, 05:28 PM

that circuit will work well with Lateral FETs as outputs.
Using Vertical FETs is risking thermal runaway.

nigelwright7557 · 26th June 2010, 09:15 PM

Quote:

Originally Posted by AndrewT

that circuit will work well with Lateral FETs as outputs.
Using Vertical FETs is risking thermal runaway.

If using vertical FETs keep the bias as low as possible to stop thermal runaway. If the bias is just enough to kill crossover distortion you probably wont even need any thermal feedback to the bias cct.

I have built about 40 amps of a similar design and all have run very well.

juma · 27th June 2010, 01:14 PM

I think we have a 100 threads about this circuit - does anyone have an idea how to stop it popping out every month or so...

Yes, it will work and survive with 20mA bias and really big heatsink but it sounds awful - LM3886 is a State of the Art class compared to that missgeburt

AudioTechs · 27th June 2010, 01:29 PM

Quote:

Originally Posted by juma

I think we have a 100 threads about this circuit - does anyone have an idea how to stop it popping out every month or so...

Yes, it will work and survive with 20mA bias and really big heatsink but it sounds awful - LM3886 is a State of the Art class compared to that missgeburt

LM3886 better than that amplifier?

How?

BrianVG · 27th June 2010, 08:06 PM

Why would it sound awfull?
I need to make a Mosfet Amp for school, LM3886 is way to easy.

juma · 27th June 2010, 10:24 PM

Quote:

Originally Posted by AudioTechs

LM3886 better than that amplifier?

How?

Easy...
Almost everything is better than that insult of an amplifier.

Quote:

Originally Posted by BrianVG

Why would it sound awfull?....

When I was 3 years old I didn't believe my dad that hot stove is not to be touched, I learned it a hard way - although those glowing circles looked so attractive...

BrianVG · 27th June 2010, 11:12 PM

I also read that this design is not able to work with the IRFP9240/240.
It has something to do with lateral/vertical. I only did learn how to use a Mosfet as a switch,nothing about lateral/vertical.

Thanks

jackinnj · 28th June 2010, 01:12 AM

Quote:

Originally Posted by juma

Easy...
Almost everything is better than that insult of an amplifier.

Now, now .... the LM3886, 3875, 4780's et alia in many configurations sound very fine.

26th June 2010, 09:12 AM	#1
BrianVG diyAudio Member Join Date: Jun 2010 Location: Louvain	Mosfet IRFP240/9240 Hello everyone, I have found a low power amplifier with the IRFP240/9240. At some fora I saw that this design has some problems like the LED and the cermet trimmer. Thank you.

26th June 2010, 05:28 PM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	that circuit will work well with Lateral FETs as outputs. Using Vertical FETs is risking thermal runaway. __________________ regards Andrew T.

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26th June 2010, 02:18 PM	#2
balaboo diyAudio Member Join Date: Jun 2004 Location: South Carolina	Despite what you have heard, the design will work just fine - make sure the bias current is between 20ma-50ma, and use a nice thick heatsink. I have a similar design as a guitar amplifier that is run at full blast with no thermal runaway issues.

27th June 2010, 01:14 PM	#5
juma diyAudio Member Join Date: Nov 2005 Location: Zemun	I think we have a 100 threads about this circuit - does anyone have an idea how to stop it popping out every month or so... Yes, it will work and survive with 20mA bias and really big heatsink but it sounds awful - LM3886 is a State of the Art class compared to that missgeburt

27th June 2010, 08:06 PM	#7
BrianVG diyAudio Member Join Date: Jun 2010 Location: Louvain	Why would it sound awfull? I need to make a Mosfet Amp for school, LM3886 is way to easy.

27th June 2010, 11:12 PM	#9
BrianVG diyAudio Member Join Date: Jun 2010 Location: Louvain	I also read that this design is not able to work with the IRFP9240/240. It has something to do with lateral/vertical. I only did learn how to use a Mosfet as a switch,nothing about lateral/vertical. Thanks

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