High Voltage BjT's for Pre-driver stages of High Power Amplifier - Overview

[AndrewT]

definitely not the 649/669 drivers

[WuYit]

maouna,
none of these is suitable.

[maouna]

there are many who claim that using a high Ft transistor as Vas, affects stability and you have to apply a higher value compensation capacitor to the Vas transistor.

i am using 100pf in my amp with +-36 volt power supply and 2sc3298 as vas and i am completely sastisfied with the performance.
if i replace it with 2sa1406 or its complement,which is said to be suitable for vas,what improvements there will be?
in a few words what would be the benefit of replacing with a high Ft ,low Cob transistor?

[WuYit]

maouna,
could you obtain any 2sa1406/2SC3600?

[homemodder]

Originally Posted by maouna

there are many who claim that using a high Ft transistor as Vas, affects stability and you have to apply a higher value compensation capacitor to the Vas transistor.

i am using 100pf in my amp with +-36 volt power supply and 2sc3298 as vas and i am completely sastisfied with the performance.
if i replace it with 2sa1406 or its complement,which is said to be suitable for vas,what improvements there will be?
in a few words what would be the benefit of replacing with a high Ft ,low Cob transistor?

Lower Cob will allow you to use a smaller miller cap, there isnt much benefit in very high ft as such but it comes down to the fact that very low cob transistors have high ft, RF transistors have cob of less than 1pf. Rf transistors do sometimes get used for audio, there are a couple of comercial designs using them in audio.

[WuYit]

homemodder,
RF transistors are not very linear in the audio range, these are.

[homemodder]

Originally Posted by WuYit

homemodder,
RF transistors are not very linear in the audio range, these are.

Some are, ask Krell, Halcro ......

Also used in modern opamps, BJTs with fts in GHZ ranges.

[villain]

Originally Posted by tiefbassuebertr

Overview of high voltage (video) BjT's, Vce >150V, currently available, for replacement in second gain stages (pre-driver) of old high power amplifier and for new designing

Do you know any high voltage BJT's for integrated circuit other than discrete devices?

[tiefbassuebertr]

Originally Posted by villain

Do you know any high voltage BJT's for integrated circuit other than discrete devices?

I don't understand this question. Mean you integrated OP-Amps like AD797 but for high voltages?

Because computer monitors and television sets with picture tubes are no longer in production, I guess, that also all BjT devices with high Vce (like the mentioned types from post #1) are obsolete and no longer available in a relatively short time.
This means, that must be by the developing of high voltage amplifier stages (VAS) other solutions realized.
Perhaps basiclly a topology realized already by the Threshold 800A output stage - go to post #14 about
800A Schematic
Four pcs. of an good known small signal device in the new outline with 45V Vce like
http://www.onsemi.com/pub_link/Colla...07-25WREV0.PDF
in serial connection delivers 180V Vce