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Re: IIgs to arcade monitor experiment



MdntTrain wrote:
One place you may have encountered it without realizing is in the
typical dual-triode "inverter" stage used in audio amplifiers to
drive a push-pull stage.

In the so-caled "long-tailed pair", the input signal is applied to
one triode which functions as both a buffering inverter and as a
cathode follower to drive the cathode of the second triode which
is a gounded-grid non-inverting stage.  The differential outputs
from the plates of the two triodes are used to drive the push-pull
stage(s) following.


Oh, Michael, you really got me here.   As soon as I read this, I
realized that I had in fact used grounded grid before when I
redesigned my Dynaco ST70... by employing a Schmitt phase splitter
prior to the push-pull stage.   The Schmitt is otherwise known as the
"long tail pair" or coupled cathode you mention.  My memory isn't
nearly as good as yours, that's for sure, despite that I'm younger
than you. ;-)

The difference that threw me is that the second triode's grid is AC
grounded only.. whereas in Ferdinand's transistor diagram, the base is
fully grounded.

Right.  The grid may be DC-biased, but as long as it's "signal-grounded"
it's "grounded grid" with respect to the signal.

Funny, the only association I have with Schmitt is the Schmitt trigger,
a positive-feedback amplifier with hysteresis, which wouldn't be very
nice in an audio application.  ;-)

Apparently "Schmitt inverter" is a non-US reference (since it was
patented in the US by Blumlein in the 1930s).

-michael

NadaPong: Network game demo for Apple II computers!
Home page:  http://members.aol.com/MJMahon/

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