Posted by Thrint [ 172.154.180.183 ] on July 31, 2005 at 18:26:50:

In Reply to: Re: Penscodes? posted by Damir on July 26, 2005 at 07:38:02:

Hey-Hey!!!,
I have a triode on the bottom, and have installed a pentode on top. Actually, I just turned the upper triode back into a pentode with a dropping R to its g2, and a cap between g2 and cathode.

I have a feeling I have turned the composite circuit into somthing with good AC impedance, or horizontal plate lines. Even better than the traditional triode-on-a-triode cascode.

The upper element of the cascode does do one important thing, it determines where the horizontal, pentode-ish plate characteristics start, relative to the Ec2 voltage. I suspect that the pentode offers a lower voltage start, and more horizontal when they happen, set of plate characteristics.

And I have a day job which gets in the way of serious experimentation.
regards,
Douglas

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