Complementary Power MOSFETs

[chermann]

You bias NMOPS, R13,14 and PMOS altogether with the optocoupler.
Using R13,14 as current sensing feedback.

Hi Patrick, thx
i thought you mean the Vgs...lol😉

the reason why i am asking is following:
i made a normal IRFP M2 since may 2022 and i am happy with the sound. compared to a F5 lateral its a little bit less clarity butthe M2 try to build a deeper sound stage. somethimes its sounding a bit to round.
now i build the exactly same amp but with the fairchild N = FQH44N10...as tungsten audio recommend in ACA premium
and the PMOS FQA9P25.
the sound is much better , i "just" look as low Ciss,Crss etc. and lowRdson to get the bias high because of my 84dB 4R speakers. i do not look at the Xdunctanc for the first step.
i get with both degeneration resistors of 0,349R a bias about 1,8Amps @ 22,7V rail.
with 2,3Amps bias with 0,278mR the get to hot after 1 hour idle 90°C..😳
my psu consist of 2x300VA the secondary get paralleld. CRC 66mF 4x0,47R 66mF.

i got NMOS VGS 3,55V PMOS Vgs 5,09V
with R13+R14 = about NMOS 4,15V PMOS 5,68 = 9,83V

kr
chris

 

[chermann]

What i do not understand is that both M2 have just 12dB gain??
i use the matched Jfets by dyiaudio store. 6-8mA as recommended in M2 schematic
M2 IRFP = 11,8
M2_F Fairchild 12,15dB

 

[EUVL]

Wrong place for your question.
You should try at the M2 thread :
https://www.diyaudio.com/community/threads/the-diyaudio-first-watt-m2x.321925/


Patrick

 

[chermann]

yep...you are right. i´ll do i at the M2 thread
M2 thread

 

[rdb64]

In case anyone cares, here are distortion measurements for 5 different MOSFET pairs:

• IRFP140 and IRFP9140
• IRFP240 and IRFP9240
• IXTH22N50P and IXTH26P20P
• IXTQ75N10P and IXTQ26P20P
• FQA40N25 and FQA9P25

In each test the MOSFETs are in an F5 amp (the exact same F5 amp) running with 22V rails and 1.3A bias. The test is a 1Khz signal (from the Akitika generator) at 1W into 8ohms.

I was surprised at how closely they all measure. The 2nd harmonic ranges from a high of .062% -- the IRFP240 pair and the IXTQ pair -- to a low of .041% -- the IXTH pair. The 3rd harmonic ranges from a high of .0067% -- the IXTQ pair -- to a low of .0039% -- the IRFP140 pair.