04-02-2025, 11:45 PM
One of the RF gurus on UK vintage Radio, and an ex Hewlett Packard RF instrument designer, said "Oscillator circuits can use transistors quite close to their Ft value. If well designed, they don't need a great amount of device gain. So it'll be a handy indication."
But most, for example, Germanium transistors generally conked out in the low MHz. The exception being the OC44 family that went to 18MHz. MESA germanium transistors like the AF139 (in a 4 legged TO18) have an fT of 550MHz and a maximum frequency of oscillation of 2.7GHz, which is pretty exceptional for Ge.
Vanilla silicon transistors can get up to the hundreds of MHz, with surface mount devices getting well into the GHz range. Good luck measuring them on an fT tester! Or the AF139 for that matter.
Craig
But most, for example, Germanium transistors generally conked out in the low MHz. The exception being the OC44 family that went to 18MHz. MESA germanium transistors like the AF139 (in a 4 legged TO18) have an fT of 550MHz and a maximum frequency of oscillation of 2.7GHz, which is pretty exceptional for Ge.
Vanilla silicon transistors can get up to the hundreds of MHz, with surface mount devices getting well into the GHz range. Good luck measuring them on an fT tester! Or the AF139 for that matter.
Craig
