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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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Old 23rd August 2012, 01:47 AM   #51
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Magnatec. ALFET Lateral MOSFETs
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Old 23rd August 2012, 01:50 AM   #52
bcarso is offline bcarso  United States
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Vielen Dank Joachim.
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Old 23rd August 2012, 01:51 AM   #53
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No I wasn't thinking TO247, more TO220.
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Old 23rd August 2012, 02:22 AM   #54
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There are only some NOS like SJ77 from Toshiba.
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Old 23rd August 2012, 02:24 AM   #55
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There are complementariness two.
Renaissas made them since two years ago so there should be some.http://documentation.renesas.com/doc...22_2sj76ds.pdf
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Old 23rd August 2012, 02:28 AM   #56
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Yes those were the ones I was thinking of. Are they just a single source?
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Old 23rd August 2012, 02:36 AM   #57
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Default Topology

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No I wasn't thinking TO247, more TO220.
I believe that the design exercise posed by Scott would be best expressed as a topological exercise. From this perspective, the size and parts count should not be a constraint, because if you want small, well, we already know we can do REALLY well with just a tiny chip.

I have built and bought numerous broadcast components utilizing the venerable 990 (some still operating 24/7 after 30 years!!!), and it still is a decent design, especially with regards to drive capability, stability, and speed of overload recovery into different line loads (300M+ of quad-star cable...). I have often thought it would be great have an updated design, considering how much better semis are these days than they were in the 990's day in the 70's.

Since Scott has also been so intimate with the limitations of IC processes and he posed the idea; I too would like to see what he and John and you other geniuses do when size/power/heat dissipation limitations are relaxed. Not to the extent that we end up with a power amp, but a true no-holds barred line-level opamp. Sort of a logical continuation of the BT thread which gave this one life...

Just my $0.02 worth as usual...

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Old 23rd August 2012, 02:36 AM   #58
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Maybe Toshiba made them too but this is a long time ago. They are pretty good though.
I use them in my privat line stage on very high idle.
I like laterals a lot. Very easy to design with.
i use them not as followers though but use the drain output. They are awesome constant current sources but Gm is not particular steep.
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Old 23rd August 2012, 03:27 AM   #59
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at op amp V, even audio line driving should be fine with few 100 MHz BJT - maybe SO-223 package for a few watts of power

the gm, parasitic C will be better than available (oversize die for the current) MOSFETs

even if the Beta isn't "infinite"



of course I'd really use the TPA6120/THS6012 DSL driver chip with GHz BJT - as a complete looped feedback amp you can have a V gain of 10x, @ 100 MHz, and with 400 mA output current, uA input the "beta" is pretty high too

Last edited by jcx; 23rd August 2012 at 03:56 AM.
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Old 23rd August 2012, 04:02 AM   #60
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Renaissas made them since two years ago so there should be some.http://documentation.renesas.com/doc...22_2sj76ds.pdf
Digikey is listing both the J76 and K213 series as obsolete. So that looks like a dead end then.

Toshiba has some high-gm FETs (even better on paper than Renesas) but they're rather low voltage and have higher thresholds than the laterals. Along with negative Vgs threshold temp coeff.
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