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Old 11th February 2012, 02:33 AM   #131
labjr is offline labjr  United States
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Quote:
Originally Posted by Nelson Pass View Post
For these purposes they are fine. Actually, in our testing they fit all our
applications.

Thanks,

It would seem they're drop-in replacements for the Toshiba JFETS. I was just wondering if they will sound as good the Toshiba since the Toshiba are obsolete and becoming rare. I wonder why Toshiba themselves didn't replace them with something better?
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Old 11th February 2012, 03:23 AM   #132
EUVL is offline EUVL  Europe
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> In any case, if you want this kind of current, you will have some mild transitions unless you want to run 20 amps or more of bias.

I don't mind the transition that much, I do care that it is too close to bias (normal listening).
If I were you I would keep the bias voltage across the R_source at say 0.3V.
That I know the diode won't kick in till I almost leave Class A anyhow.

But why not try 3497/681 ?


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Old 11th February 2012, 04:46 AM   #133
NYCOne is offline NYCOne  United States
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Default Balanced Rail Voltage Choices - more Class A

NP -

When I built my Balanced Cascoded F5, I chose the lowest rail voltages that had a flat transconductance plateau for the MOSFETs (2SK1530 and 2SJ201 at 16V). I did this so I could crank up the current and have more power in Class A at a given wattage for each output device.

I noticed you were recommending higher rail voltages and paralleling devices for more power, but wouldn't more current help with Class A?
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Old 11th February 2012, 05:05 AM   #134
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I'm sorry !
Am I right, FQA12P20 was a Discontinue Product ?

Thanks !
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Old 11th February 2012, 11:29 AM   #135
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Old 11th February 2012, 11:34 AM   #136
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Absolutely. Fairchild doesn't even list it anymore. No stock at Mouser, no stock at Digikey.
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Old 11th February 2012, 11:48 AM   #137
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Old 11th February 2012, 11:49 AM   #138
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You could substitute FQP12P20 which is a TO-220 device -- the transconductance is a tiny bit lower and the device has a higher thermal impedance...
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Old 11th February 2012, 12:07 PM   #139
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Quote:
Originally Posted by jackinnj View Post
Lateral MOSFETs have half the input capacitance of the vertical ones but less than a quarter of the steady state current carrying capacity.
Ah, but even at 1S to 1.5S, the power diode trick would save a couple of volts.
With oldy 600mW JFET cans at the entrance, 4 laterals in parallel would be near equivalent.
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Old 11th February 2012, 12:23 PM   #140
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Will this trick work on f4 like buffer?
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