IRF130, 9130 drive?

[maxpou]

Hi,
i would to know is driver stage with a current of 10mA can drive 3 IRF130 in parallel? Thank you! Maxpou

[darkfenriz]

If the stage preceding output mosfets is single-ended VAS, than it cannot source more than 10mA, that's low for driving mosfets.
But it should be workable, contrary to bipolar output mosfets do not require any DC current to work, with 10mA expect some rise in THD with frequency and limited slew rate.
Adam

[AndrewT]

Hi Max,
what is the capacitance of the IRF130?

The driver has to charge those three capacitances.
At high audio frequencies this is a surprisingly large current.
10mA might be too little.

If it were a follower, then it goes into ClassAB, but dissipation at high frequencies becomes the problem, particularly during testing.

[maxpou]

Hi,
the Ciss for IRF130 is 650pf and IRF9130 is 860pf. I have 2 drivers one on negative rail and one on positive rail ( i don't know the name of this configuration). The operation class is AB with 100 to 150 mA. Thank You! Maxpou

[AndrewT]

Hi Max,
you might find this spreadsheet useful or confusing.

Look at 2n2F and 20kHz for loading in the audio band for your 3pair from a 10mA VAS.

Now look at 2n2F & 100kHz. How low does the Vpk need to be to keep the Ipk below 10mA?
A classA stage does not drive a capacitance particularly well at high frequency.

The problem you will have is deciding what capacitance the FETs present to the VAS.
There seem to be many conflicting views.
Then deciding what Vpeak is sent to the FETs when testing and when listening to ordinary/extra-ordinary music/sound effects.

You can avoid the dilema by using a lower VAS current and inserting a follower that goes into classAB when the current demand inadvertently goes too high. At least it will sound better than when clipping. But does the follower sound better on ordinary signals?

[maxpou]

Thank You Andrew,
I would like to also know if are of good mosfet for poweramp?
thank you! maxpou

[AndrewT]

I can't translate the question!

[maxpou]

excuse me for my english,
IRF130 and 9130 are a good mosfet for sound quality, because i replace 2sk1058 and 2sj162 for these. thank you! Maxpou

I hope that I clarified my question!

[AndrewT]

I can't help.
We have no information from the schematic other than VAS & output quiescent currents and number and type of output devices.

[maxpou]

Hi Andrew,
my schematic is the Buzquito of Jean-Marc Plantefève ( http://perso.orange.fr/jm.plantefeve/sche.html ) Thank You! Maxpou