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-   -   Complementary Power MOSFETs (http://www.diyaudio.com/forums/solid-state/224827-complementary-power-mosfets.html)

jkuetemann 2nd December 2012 04:24 PM

Complementary Power MOSFETs
 
Aside from lateral MOSFET types specifically marketed towards audio are there any complementary MOSFETs that are reasonably well matched? I've been looking around at various products and data sheets and it seems that there aren't many complementary power MOSFETs out there that aren't laterals.

Can you guys recommend pairs known to have reasonably complementary parameters, even if they span different product families or even manufacturers? Preferably readily available current production parts, if possible.

I'd like to order for my stock some different parts to experiment with but since I've been a BJT kind of guy for so long I'm not familiar with what may be available.

Tekko 2nd December 2012 04:29 PM

Since all vertical mosfets i know of are made for switching, there are no true complementary ones, just ones that are very similar, but not close enough to be true complementary.

For example, the P channel device always have atleast 0.1 ohm on resistance while the N channel one is a few tens of milliohms.

DUG 2nd December 2012 05:37 PM

In MOSFET selection for linear amplifiers Rds(on) is one characteristic that I totally ignore.

I would hope I am not listening to music that is hitting the rail supply. :)

Gate capacitance, etc is far more important to a complimentary MOSFET matching.

Max V, max I, SOA, Pdiss, don't need to match, just make sure they exceed requirements.

Transconductance should be as close as possible.

IMHO :)

jkuetemann 2nd December 2012 07:31 PM

OK, perhaps I'm asking the wrong questions. I'm still interested to get opinions on what devices are 'close enough' to use where typically complementary devices would be used, be specific.

As far as selection goes, let's see if I'm on the right track.

1) Based on application choose a P channel device that meets or exceeds the requirements since there are fewer of those from which to choose.

2) Based on the P channel device characteristics then begin to seek a 'best fit' complement from the plethora of N channel devices.

So, based on my initial selection process what are the parameters to try and match? What order to consider them in? As DUG suggested certain parameters can take a back seat while others are more important. I'd like to set it straight in my mind what is important and what can be safely ignored.

CBS240 2nd December 2012 09:29 PM

I use FQP50N06 & FQP47P06 in my EC mosfet stereo amp. They are planer stripe devices, very rugged, very cheap.;) I understand the fabrication process is a bit cheaper than for hex type and similar 'cellular' die structures. Stear clear of certain architectures such as Trench fets, U-fets, and similar types. These are not suitable for analog operation.

Because the P-ch has a different input capacitance and gate charge requirements vs Gm than the N-ch, I like to use a totem pole driving stage for each gate, something similar to a diamond buffer, that provides a seperate path for gate charge from the N-ch and P-ch devices to the driver stage.

jkuetemann 5th December 2012 11:11 PM

No one else has any suggestions for V-FET 'pairs'? Based on some searching of datasheets I think these may be candidates..

http://www.fairchildsemi.com/ds/FQ/FQA36P15.pdf
http://www.fairchildsemi.com/ds/FQ/FQA46N15.pdf

nigelwright7557 5th December 2012 11:19 PM

IRFP240/9240 are commonly used together.

Feedback takes care of a lot of differences.

DUG 5th December 2012 11:40 PM

Jason (post 6),

http://www.fairchildsemi.com/ds/FQ/FQA36P15.pdf
http://www.fairchildsemi.com/ds/FQ/FQA46N15.pdf

Can't seem to be found.

jkuetemann 6th December 2012 12:19 AM

Quote:

Originally Posted by DUG (Post 3272144)

Sorry, formatted my URLs incorrectly. Thanks for the correction.

Junm 7th December 2012 02:27 AM

Quote:

Originally Posted by DUG (Post 3267267)
In MOSFET selection for linear amplifiers Rds(on) is one characteristic that I totally ignore.



Gate capacitance, etc is far more important to a complimentary MOSFET matching.

Transconductance should be as close as possible.

IMHO :)

You mean Crss, Coss and Ciss...what is the most important among the 3 to consider for a class ab PP amp?


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