The interesting Luxman stage

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Folded cascode

Oh great...... The Nelson Pass amplifier designer school. Free tuition! Why don't you look at Mr. Pass's design articles at his websites and do a search on "cascode" on the forum search page. I think it is a little much to ask a question that broad to anyone on a forum.

HarryHaller, it's costs you nothing to be humble and nice...

Mr Nelson Pass seems to be a decent guy and I imagine he will answer if he feels like it and/or when he got time. I appreciate if any person have something to say in this matter.

I have searched but I haven't got any "meat on my bones" as we say in Sweden, about just this particular circuit.
I have redrawn the schematic to see better. It seems to be a modified folded cascode circuit. I haven't figured out the difference (in performance) between a

regular diff stage + folded cascode


diff stage + a regular high gain stage with regular cascode. like my overkill phone amp (see my homepage)

Have you checked the advanced cross connected emitter follower?
I could be wrong ... as i have not analyzed the circuit (no no, no sims!) yet but you move you dominant pole away from the input stage (the currentmirrors) onto the collector of 2SA1360 and the 2SC3423.
You also get a higher gain this way because of the currentmirror. The currentmirror works as a active currentsource driving the cascode pair...
This way you use both legs of the input diff pairs. This will also double your slewrate in the circuit.

You mean 2sa1360 and 2sc3423?? Folded cascode

This folded cascode is sitting on top of the cascodes (C1815 and A1015) for the jfet diff amps. I could explain the circuit but it would cost too much time and effort and people will complain about me anyway... I'm I the only one who thinks there are way too many parts in this thing?

uuuhhh!!? You mean the feedback loop ..wierd!

The feedback loop is the coolest thing about this amp. You can use a small film cap and still use low value feeback resistors so as not to run into input capacitance problems with the diff pair feedback input. I have used this several times and I love it.

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