IRF(9)610

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#27
fpitas said:
If you are looking for a substantial improvement in performance, it might be easiest to cascode the output stage.
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... but would if not be nice to have a 200V 2A 50W 50pF mosfet, maybe it is out there, and maybe someone finds it.

Also a 200V 1A 20W 20pF pair may exist.

The problem is that these things are not design for linear applications, most (if not all) are specified and designed for switching, but there may be some gems to find.

As listed in post #1
FdW said:
http://www.fairchildsemi.com/ds/FQ/FQP3N30.pdf FQP3N30; 55Watt 175pF 5.5nC
http://www.fairchildsemi.com/ds/FQ/FQP3P20.pdf FQP3P20; 52Watt 190pF 6nC
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these are (in my opinion) already an 'improved' pair of mosfet's, both 50W and about the same input capacity, that counts as a result 🙂
 
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#28
The Fairchild parts are an improvement, no doubt, but with cascode you could use a low voltage part for the bottom device, and perhaps get even lower input capacity. You would also minimize the Miller capacity seen at the input.
 
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#30
fpitas said:
The Fairchild parts are an improvement, no doubt, but with cascode you could use a low voltage part for the bottom device, and perhaps get even lower input capacity. You would also minimize the Miller capacity seen at the input.
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Yes... 🙂 but that's not the point, and in the particular design that I have here a cascode is not possible. Anyway, lets give it some time and maybe someone (or something) will popup and show us the part that we always wanted (it is near xmas).
 
#31
#37
Bensen said:
Frans,

Have a look here, see post number 9! Could be helpfull for you?

http://www.diyaudio.com/forums/soli...osfets-complementary-pairs-2.html#post3700935
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Thanks for showing/reminding me of this.

Jay said:
CHOICE OF COMPLEMENTARY PAIRS

When transconductance is not required, I found that ZVN3310/ZVP3310 is the best. They have small capacitance and a good match (80%). Max 40pF for ZVN and max 50pF for ZVP.

#2 is BS170 and BS250 which has comparable small capacitance but unpredictable matching. But even tho these are not meant as "complementary" pair, they are widely used in telecom/radio equipments. I use this pair for my projects.

#3 is ZVP2110G/ZVN2110, less than 100pF. Not really complementary (75%). Fetzilla uses only the ZVP so there is no need for matching, just small capacitance.

#4 is VN1210/VP0808, less than 150pF and are very good match (83%). Also has good transconductance (above 0.2S). This is used in JLH89.

#5 is ZVN4424G/ZVP4424G, less than 200pF. Pretty good matching (91%). The transconductance is probably very high but doesn't match well (31%) so only for "VAS".

#6 is K213-6/J76-9 which is typically no more than 120pF. But useless transconductance (too small).

Now when transconductance is critical such as in a driver or preamp output, I consider useful transconductance starts at 0.7S. K2013/J313 is the smallest (typ. 0.7S/210pF), but may need reinforcement and/or paralleling for good current taste, and not really matched (69%).

IRFD120/9120 has waay too high capacitance (450pF).

IRF9610/710, at slightly above 1S and 150pF is actually the best "all round" device, but this also puts them in a difficult position for very demanding listeners (It is either too low transconductance or too high capacitance).

IRF 510/9520 (typ. more than 2S) is prime for transconductance (and is the biggest mosfet suitable for VAS/driver), while maintaining acceptable (to most listener) capacitance typically below 300pF. This can be used in class-A amps (Ayre V3 is an example).

IRF632/9630 is my choice for my TSSA output (typically higher than 3.5S, less than 800pF). For a mixed mosfet-BJT output (BiGBT?) they can also be used (73% matched). Dr Jagodic used IRF630/9630 for DOGC-H, but they are terribly matched imo (36%).

IRF530/9530 has higher transconductance and was used by Dr. Jagodic for DOGC MK3. In my prediction they are terribly matched (39%). I don't know why Dr. Jagodic (Boraomega) switched to IRF630/9630 (equal predicted capacitance) in later DOGC-H. I have built them but never simulated. I guess IRF632/9630 will perform better.

IRF640/9540 is also a good match (93%), but they are from different voltage classes so I guess the numbers are not reliable for comparison. They are still very good match but IRF632/9630 are measured and sound better in my applications.
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It seems that 'VN1210/VP0808' is a candidate for my list, I'll check it out.
 
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