differential cascode patented in 2007

[Jaap]

I did find a recent patent (2007) here: Single Stage Balanced Voltage Amplifier - US 2007/0296492 A1 - IP.com

Any comments ?

I like to try it with 6H30 or 6N6P, any suggestions for resistorvalues / B+ ?

[piano3]

How on earth can someone be granted a patent for this?

[SY]

Originally Posted by piano3

How on earth can someone be granted a patent for this?

It hasn't been granted. It's an application.

[pieter t]

Piano,

When we talk patents we think someone has come up with something original, not done before.
US patent system is a bit different; "patents" are often only used for commercial reasons, to prevent competitors from doing the same.
Audio Note's interstage transformer in their dac's is an example here in Europe.
When you investigate what it means most of the time the "patent" is valid in the US, or Europe, or just your own country. Patents which cover the whole world are the most expensive.

Pieter

[Arnulf]

Originally Posted by Jaap

I did find a recent patent (2007) here: Any comments ?

Why isn't output taken from the bottom of the CCS ?

Oh and I believe something similar (but with resistive load if I'm not mistaken) was posted here about 1 year ago, again a differental pair of triode cascodes.

[smoking-amp]

Cut and paste out of a textbook. Nothing even clever about it. But since someone successfully re-patented the Darlington circuit with a tube in it, I guess the patent office doesn't expend much manpower on tube technology searches. Nice to have money to burn on such silly patents. This is probably just advertising-hype driven. If they don't have anything novel, they just fake it.

[Mother of PEARL]

While the implementation I worked up some 15 years ago is singe-ended, a little study of that work and comparison with Fig. 2 in the patent app shows some real similarity in the f/b to the middle grid. I like mine better though ;-).
Here's the schematic http://www.pearl-hifi.com/06_Lit_Arc...scode_RIAA.pdf

Bill @ PEARL

[smoking-amp]

Oh, the patent has the cascode grids ultralineared? I couldn't see that in the tiny picture in post #1. At least it has something more than a plain vanilla cascode then. Still, UL'ing a cascode has been around for a while, as Bill just demonstrated.

Another issue is that 3 tubes stacked up is simply impractical and dangerous, considering the high B+ required, and all those floating filament supplies required. Putting some Mosfets up top sides would make the thing more practical, but nothing new though. I seem to recall Janneman posted a Fluke HV calibration amplifier that used that setup.

[Jeb-D.]

Originally Posted by smoking-amp

But since someone successfully re-patented the Darlington circuit with a tube in it

Do you know the patent number by any chance?

[Mother of PEARL]

Hi:
Click the link in the first post to get the patent and no the grids in the first implementation are not "ultra-lineared", the thing is just a straight ahead, diff cascode with active plate loads.
For something rather more interesting pull down this PDF http://www.pearl-hifi.com/06_Lit_Arc...n_a_Work_2.pdf and see page 24; some work a self-balancing diff stage that applied any common mode error to the "long tail" current source with the result that much higher and stable CMRR could be achieved over the life of the tubes.

Bill @ PEARL