Hi The tube cascode has it’s own issues. Setting up a tube circuit for the sort of isolation we are talking about here is very difficult.
Bob > On Jul 6, 2022, at 9:46 PM, glenlist via time-nuts <[email protected]> > wrote: > > how about grounded grid ? > > Bob can you get better isolation with a vaccuum tube cascode than a solid > state cascode ? > > -glen > > On 07/07/2022 15:22, Bob kb8tq via time-nuts wrote: >> Hi >> >>> On Jul 6, 2022, at 1:53 PM, Richard Karlquist via >>> time-nuts<[email protected]> wrote: >>> >>> The 2N5179 has high base spreading resistance (decreases isolation). >> As does sticking a resistor (even a small one) in series with the base …. >> Yes, inductance >> is even worse. >> >> For “best isolation” in a cascode you very much want the base of the common >> base >> stage nailed to ground. Typically “lower” Ft transistors with a decent base >> structure >> are the best choice for the common base stage. Both stages benefit from low >> 1/F noise >> in the audio range if this is for a phase noise test se >> > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe send an email to [email protected] _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe send an email to [email protected]
