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 set. This is why people use what would normally be considered “audio” transistors …. Bob > > --- > Rick Karlquist > N6RK > > On 2022-07-06 12:18, ed breya via time-nuts wrote: > >> My favorite VHF Q is the good old 2N5179 or similar, but it appears you want >> something in surface mount, and not obsolete. I'm not familiar with the >> modern SMT stuff. If your present transistors are working, but just need a >> bit more stability, it seems it should be OK with the right scheme, and not >> the transistors' fault. >> >> Ed >> _______________________________________________ >> 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] _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe send an email to [email protected]
