Bridge With IRF 540 & IRF 9540

[ilimzn]

I don't think so, it was at least a 100 times...
BTW, what do you think about the combination IRFP9240 to IRFP340 ?
Mike

That's my favorite one for rails over +-50V. Kind of a poor man's 2SJ201/2SK1530
The thing is, one needs to be careful with second sources and improved versions - for most save the IR parts, the complementarity does not hold too well. I should really look into some of the newer Fairchild and ST parts, though. Especially for the lower current ones...

 

[ilimzn]

Thanks for reply & advice.
( IRF 540 x 2 ) & IRFP240
Which is more power & more stable ?
Regards,
Myanmar

IRFP240 is roughly equivalent to IRF640 (IRFP240 is a 200V part).
The difference is in the case and technology:
IRFP240 has a junction to heatsink thermal resistance of 1.07K/W and a maximum dissipation of 150W at 25 degC.
IRF640 has a junction to heatsink thermal resistance of 1.5K/W and a maximum dissipation of 125W at 25 degC.
What does this mean? If you have an infinite heatsink, at 25 degC, and run your MOSFETs at their maximum die temperature of 150 degC, your IRFP240 could dissipate a maximum of about 117W, and an IRF640 will be able to do 83.3W for the exact same conditions. That's the theory. Things get a bit more difficult in practise - for the IRFP240 it is fairly easy to achieve the quoted thermal resistance using normal mounting methods. Not so for the IRF640 - this is only achievable using a clamp (not mounting it with a screw).
That being said, the IRF640 has (surprisingly) better SOA than the IRFP240, due to it being slightly newer technology (IRFP is repacked IRF dies that used to be in TO3 cases, first generation HEXFET). For instance, IRFP240 has 3A@100V 10ms, IRFP640 has 4A at 100V 10ms. So, two IRF640 will definitely be better than one IRFP240 at being robust and dissipating heat, BUT they will have lower (but more linear!) gm due to the mandatory inclusion of source resistors, for proper current sharing. These will have to be quite high (0.33-0.5 ohm).
If you can limit yourself to +-50V rails, IRF640 and IRF9540 will be better complementaries than 640 and 9640 or 540 and 9540.

There is one very important thing with IRF parts. There are many second-sources, and some are not as good as the originals. There are some that are rated only 80W instead of 125. For instance, ST IRFP640 has same maximum dissipation but SOA only 2.5A @100V 10ms. Fairchild version has SOA 3A @100V 10ms, but has reduced maximum dissipation (110W), etc.
With IRFP parts, most second sources are actually slightly better than the originals.

 

[myanmar]

Thanks for explain.
Now. I stop to change two rail in IRF540 & 9540.
I will use other mosfet if i want to use two rail.

+-50V rails are the absolute maximum limit for 540/9540. For more than that you need 640/9640, but you will need 2 pairs per amplifier. It would be a better idea to use a slightly higher rail voltage for the driver stage (about 5V higher) to get extra power and reduce heat.

Can I use only rail voltage for the driver stage (about 5V higher) ?
Can I use 40V higher rail voltage for the driver stage (that is +/- 80V ) use with complementaries IRF 640 or IRFP240 ?



I want to know which is more linear & HiFi ?
Use with All N-channel ( like Quasi AMP )& Use with P&N channel (complementaries).

Regards,
Myanmar.

 

[richie00boy]

The driver stages only need to be about 10v higher than the output rails to overcome the Vgs threshold, anything more is a waste.

As for which is best n-channel or complementary... that's a big can of worms with fierce fighters for each side!