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Old 26th January 2009, 06:44 AM   #11
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Stefanoo,
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do I need TO220 devices and high bias, or i can just Bias as much power as the TO92 can take (wich is about 300mW)?
According to the data sheet, 2SC2240/2SA970 can take 300mW all right (without telling how long, in audio most max ratings are irrelevant anyway), but I would not like to listen to the sound they produce under such condition.
Power dissipation is probably the limiting factor even with 2SC5171/2SA1930, at 25mA being 750 mW.
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Old 26th January 2009, 10:59 AM   #12
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This is one of the few issues with 2SC2240/2SA970:
.. Can not take very much power!
I have seen figures of 200mW, max.
Less than normal TO-92, like BC550C/BC560C ~500mW

Otherwise, 2SC2240/2SA970 can work att very high voltages .. with matching reduced, low current, of course.
120 Volt C-E !!!, where BC550C/560C are only 45 Volt ..
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Old 26th January 2009, 11:31 AM   #13
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Hi guys,

i have followed the Lumba's suggestion and increased the output bias to 69mA.
Outptut devices are still running pretty cool, no need for heatsink.
Since i like the sound of the IRFs 610/9610 parts, i am going to use them on the output stage.

The problem is: switching from the low power BC to the IRF gives rise to overshoots.
I don't know, i will try to play around this.
I think that cascoding the 2 BJTs might help this, or i will see if i can do something else.

do you guys have any suggestion?

The compensation would be my LAST resource!
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Old 26th January 2009, 12:26 PM   #14
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Stefanoo,
this configuration would significantly linearize your output stage.
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Old 26th January 2009, 04:47 PM   #15
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Try this one, not sure what you driving, but this one can drive 1K loads with lower than -120db, mainly second. Best performance is obtained by using very high gain bjts but that have very low cob. Can suggest some but I dont know if youll be able to get them. To adjust output offset simply tweak the output resistors, no input offset. Tweak the currents depending on the transistors used, sounds excellent. What comes in is what comes out, wire with gain.
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Old 26th January 2009, 06:10 PM   #16
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sorry, but it doesn't let me zoom the picture you have atached.
May you do it again? I can't see it.

thanks.


P.S. just for curiosity, what are the transistor's type you were referring to?
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Old 26th January 2009, 10:14 PM   #17
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I try again, this time as bitmap. I use in general 2sc3495 and complementary, ksac1381 and compl. high gain group also works ok.
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