IRFP240&IRFP9240 power amplifier schematic

mos

Member
2005-08-18 1:25 pm
IRFP240&IRFP9240 power amplifier schematic

Hi, I've searched on this forum and on the internet a power amplifier(250W-300W) schematic with IRFP240/IRFP9240, and I didn't found one.Can you help me with one?:confused:
I wan't to use this amp in home but it should have the same performances with PA amp.
Please scuse-me if there are some mistake's, but my English isn't so god.
Thank's a lot, Vlad.
 
rudi said:
Here is one for you. been wanting to try it for some time now. but i am sure this will heat up any room.. what I found interresting is the feedback cicuit.


The feedback is just using designed around a DC servo, but the chip they are using (TLO71) is not too good for that application. Something like a LF411 should do much better.



Carlos
 
These devices, the IRFP240/9240 have around 4-5V , Vgs on, so you will waste this much in supply voltage above Vas losses unless you operate them common source from the rails. A small source R is necessary unless you can match them very well and have good heatsinking and thermal feedback control of their operating conditions. A price to pay but, when you consider that at 250W/8ohm peak voltage is 64V and 5V extra is 300W!


I have a design which will work with cascode input stage. I just need about a week to put the finishing touches.

Cheers,
Greg
 

Nelson Pass

The one and only
Paid Member
2001-03-29 12:38 am
amplifierguru said:
These devices, the IRFP240/9240 have around 4-5V , Vgs on, so you will waste this much in supply voltage above Vas losses unless you operate them common source from the rails.

I routinely allow that much loss, as the capacitance of the Mosfet
goes to hell below about 5 volts D-S anyway.
 
Maybe its my eyesight going bad. But I think I saw IRF540 and IRF9540 mosfets as output devices?

They're TO-220 devices, not sure if they can substain what you want at 250W to 300W. You would need alot of them to spread the dissipation to a decent level for long term use.

A.Holton's AV400 would be a good choice as suggested. 400 watts into Class AB. And he uses IRF9240 and IRF240 as recommended devices too. All fitting your requirements.
 
rchua77 said:
Maybe its my eyesight going bad. But I think I saw IRF540 and IRF9540 mosfets as output devices?

They're TO-220 devices, not sure if they can substain what you want at 250W to 300W. You would need alot of them to spread the dissipation to a decent level for long term use.

A.Holton's AV400 would be a good choice as suggested. 400 watts into Class AB. And he uses IRF9240 and IRF240 as recommended devices too. All fitting your requirements.


You only need to substitute these with the FET of your choice. I.e. IRFP240, IRFP9240 etc. Just gotta match the voltage and the power you want. BY running somethin like MJE350 / 340 in the driver and pre-output stage you could run 8 to 10 FETs per board.

Cheers
 
mos said:
Hy! Quasi, can you tel me if in your schematic i can use IRFP240&IRFP9240.If I can, what power it will give?Thanks a lot.Bye.


+/- 65 volt rails will give you around 190 watts into 8 ohms and depending on your power supply around 320 watts into 4 ohms.

To do this safely you will need 4 pairs of IRFP240/9240 per amp board. You will also need to change most of the transistors in the amp to higher voltage types and the drivers and pre-output transistors will need a higher power rating (suggest MJE350/340) mounted on small heatsinks.

Cheers
 
Hi Quasi,

Yes I've seen this design before - it's rather more complex than mine but yes you can stretch it up to any power. It's been discussed on this forum before and has some stabilisation issues. I think if R10,R14 were 0R that RC compensation may have some effect. Also the output L should have a parallel R or it will really ring with C loads.

Cheers,

Greg
 

mos

Member
2005-08-18 1:25 pm
Re: rchua77 supporting

mandat said:
I agree, that AB class amp is only one acceptable solution for power amplifier rated at 400W. Some time ago there was available schematic of Holton’s multiMOSFET power amplifier at his homepage. I have a copy of this schematic and I can send you by e-mail, if you want.
http://www.aussieamplifiers.com/

Yes, I would like to send me a copy. My mail adress is [email protected]
I found this schematic http://users.swing.be/edwinpaij/ampli_mosfet_simple.htm and I ask you what do you think about it, and what power should it give.
Cheers,
Vlad.
 
IR AN-948

I had a copy of this application note which descibed a power amp using these FETs. It was so full of errors though itseems to have been pulled from the site. I will try to find my printout and post it(with corrections). They gave me 10 or was it 20 of each FET for finding all the typos.