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Old 9th February 2012, 10:53 PM   #101
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fdlsysl you are welcome
here is the link
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Farnell still sel the FQA12P20
the FQP19N20 is what I use since last August.
Also from Farnell.

But if you can get them from somewhere else I suggest you do so as Farnell stuff does not match preaty well (most probably loads of batches mixed up)

IF I was so luky to live on the other side of the pond I would buy direct from Farchild
I just got 3000 transistors from there they cost me about £60 + 120 P&P and another bill arived today for £32 customs charge.
I know that they will match well but the charges are rape.

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Old 10th February 2012, 01:04 AM   #102
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Are the diode sacting as a sort of bypass capacitor for the curren tthrough the fets, essentially providing a resistance free(or greatly reduced) path for curren to output? Sorry to dumb down the , thread, just tryin gto wrap my head around it.
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Old 10th February 2012, 01:05 AM   #103
JZatopa is offline JZatopa  United States
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Had a question about the LTC4358 but I think I already answered it.

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Old 10th February 2012, 01:24 AM   #104
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I'm wondering will the diode trick on the o/p trannies benefit a stock F5...
Just wondering....E
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Old 10th February 2012, 01:29 AM   #105
eyoung is offline eyoung  United States
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you could be like me and stupid down...
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Old 10th February 2012, 03:13 AM   #106
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> Are the diode sacting as a sort of bypass capacitor for the current through the fets, essentially providing a resistance free(or greatly reduced) path for current to output?

In a way yes, also a bit like the cathode resistor bypass caps in tube circuits.
The difference is that the cap's impedance is frequency dependent and it introduces a phase shift, but it is continuous and the resulting transfer function is smooth. The diode is voltage (or MOSFET drain current) dependent, acts like a clamp on the maximum voltage across R_source, but does introduce a sharp discontinuity when it kicks in, the latter being a bit like an amplifier's transistion from Class A to Class AB.


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Old 10th February 2012, 05:05 AM   #107
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Patrick, I kinda see it as a weird sort of current based Class H design, but with the obvious difference of combining the two or more rails as one and two or more sets of output devices as one, but the diode plays the switching role by doing the "magic"...

just a strange point of view...

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Old 10th February 2012, 05:10 AM   #108
EUVL is offline EUVL  Europe
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Looking at post#18, 19, I personally much rather use the UHC solution (K3497/J618).
I can easily reduce R_eff further by using 0R15 o reven 0R1 R_source.
And I get much more linear transfer function all the way up to 12A per FET.

If one then worries about dissipation, one can always cascode the output FETs as well.

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Old 10th February 2012, 08:30 AM   #109
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Quote:
Originally Posted by Bksabath View Post
rape charges
Same story on this side.
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Old 10th February 2012, 10:22 AM   #110
AndrewT is offline AndrewT  Scotland
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Anyone know if Linear Systems started making the LSK170
there was a group buy of lsk170 etc about 2 to 3 years ago.
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