I don't understand your question.
fT is frequency where hFE of BJT is 1. Ideally, hFE don't change if frequency change. That's what we want
.^sorry for the out of topic question. i just need a simple answer like how does it affect the operation stability of an amplifier, or sound quality if the pre-driver, driver, output transistor configuration does not follow an Ft order like the one mentioned above considering audio signals and its harmonics are far too low from the lowest Ft specs (30 MHz) among the given transistors?
No, I have different compensation than OS design. And my amp is stable
Jaagut, as long as fT >> 20kHz, I think THD is not affected by fT.
Sim result show, high fT can give more slew rate in CFA topology.
Here is the modified CFA-X V1.2 but be careful ,my power supply is +/-50V!
Attachments
there is no simple answer, why do you think Japanese amps used semicons with high fT's and hFE's that doesn't droop too much with current?
you can run simulations and try using trannies that are low fT's and low hFE's and see what happpens....
The B-C leakage of the transistors will be dominant in the distortion of this circuit. It seems like a lot of extra transistors for not much gain when you consider this. It could be improved, but it would have a lot of transistors. It could be a more-transistors-less-resistors approach.
I would start with Dado's GainWire where I helped to lower the B-C leakage using Baxandall-cascoded current mirrors.
I have a 6N3P buffer that runs on 50V rails, so I'm sure a CFA could be made with a tube input. 180V rails could certainly be done, but with special requirements.
