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RE: Rosenblit Also Got This Wrong

Posted by PakProtector on June 13, 2021 at 11:47:53:
It helps me to think of the LTP as a composite. It is like a grounded cathode amp for the input stage, and a grounded grid for the second. They are joined( ideally ) at the cathode node and taken to ground by a current regulator.

It does not matter what the idle current is, or how it is shared( until a lack of voltage outptu somewhere comes into play). Raise the grid of the input stage and the current through that stage increases. The cathode follows it, driving the second half towards cut off.

There is some solid math out there to describe the behaviour when the cathode load is resistive.

Gain plate to plate is about u, gain for a single plate to ground is half of u. From the time when a high gain pentode drove a split load( a fairly easy load ), another stage ahead of it was usually employed( the 5-20 comes to mind). Laurent and the 6AN8/7199 made things slightly lower in parts count.
cheers,
Douglas