Which transistor for my amp?

OliverD · 24th February 2003, 01:01 AM

I'm looking for a readily available, "modern" transistor for new my amplifier's gain stages. The problem is that I'll have about +/- 85 V rails, so the transistor should have a Vce rating of about 180..200V. I need both NPN and PNP.

Other requirements:

-> Ic(max) ~ 100mA
-> Ptot ~ 1W
-> fT ~ 200 MHz
-> hfe(typ) ~ 200...400
-> low noise, good linearity, low Cob

Do you have any suggestions?

For driver and output stages, I already setteled for 2SA1930/2SC5171 and 2SA1987/2SC5359.

sam9 · 24th February 2003, 04:42 AM

check out sound.au.com. Somewhere in the downloads is a compilation of transistor data. About 1400 items.

OliverD · 24th February 2003, 12:03 PM

Thanks for the link! It's a big collection of mostly 2N... types...

Unfortunately, there was no transistor that meets my requirements... Maybe I need to redesign my input stage to run from a different (lower) supply voltage...

Any more suggestions?

till · 24th February 2003, 12:10 PM

i would use parametric search at onsemi or fairchildsemi. com. But with that high voltage i can´t find that high hfe

Christer · 24th February 2003, 01:06 PM

Not quite what you want, but 2N6517/6520 from ON will at
least handle the voltage and Pd required. I think it is very
difficult, if at all possible, to make high-hfe devices for very
high voltages.

davesaudio · 24th February 2003, 01:52 PM

make your own darlington pair to get the gain?
(yes has some drawbacks- I know, just tossing ideas)

OliverD · 24th February 2003, 04:31 PM

Thanks for your suggestions...

2SA1376 + compl. is the only device that would fit perfectly from the specs, but I doubt whether it is suitable for audio... And it seems to be obsolete...

Seems I have to redesign my input stage

Christer · 24th February 2003, 05:26 PM

Not that I know what design you had in mind, but a common
way to deal with the problem that may perhaps be a feasible
redesign in your case is to use lower-voltage transistors
with high hfe and then cascode these with high-voltage
transistors.

OliverD · 2nd March 2003, 10:14 PM

Yup, I'll cascode the VAS and driver stages, but I don't want to cascode the input stage in this particular design. Maybe I'll just provide an additional (lower voltage) power supply, I don't know yet.

Anyway, to revive this thread, does anybody know a modern replacement for 2SA1376/2SC3478? Datasheet is here: http://www.necel.com/discrete/images/pdf_e/TC-3529.pdf

Also, I want to replace the famous Toshiba 2SA1145/2SC2705 as used by LCAudio. Datasheet available here: http://www.lcaudio.dk/2SA1145.pdf

Can anyone help?

24th February 2003, 01:01 AM	#1
OliverD diyAudio Member Join Date: Nov 2002 Location: Germany	Which transistor for my amp? I'm looking for a readily available, "modern" transistor for new my amplifier's gain stages. The problem is that I'll have about +/- 85 V rails, so the transistor should have a Vce rating of about 180..200V. I need both NPN and PNP. Other requirements: -> Ic(max) ~ 100mA -> Ptot ~ 1W -> fT ~ 200 MHz -> hfe(typ) ~ 200...400 -> low noise, good linearity, low Cob Do you have any suggestions? For driver and output stages, I already setteled for 2SA1930/2SC5171 and 2SA1987/2SC5359.

24th February 2003, 01:52 PM	#6
davesaudio diyAudio Member Join Date: Feb 2003 Location: GTA	make your own darlington pair to get the gain? (yes has some drawbacks- I know, just tossing ideas) __________________ intentionally blank

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24th February 2003, 04:42 AM	#2
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	check out sound.au.com. Somewhere in the downloads is a compilation of transistor data. About 1400 items.

24th February 2003, 12:03 PM	#3
OliverD diyAudio Member Join Date: Nov 2002 Location: Germany	Thanks for the link! It's a big collection of mostly 2N... types... Unfortunately, there was no transistor that meets my requirements... Maybe I need to redesign my input stage to run from a different (lower) supply voltage... Any more suggestions?

24th February 2003, 12:10 PM	#4
till Banned Join Date: Apr 2002 Location: Germany, Clausthal	i would use parametric search at onsemi or fairchildsemi. com. But with that high voltage i can´t find that high hfe

24th February 2003, 01:06 PM	#5
Christer diyAudio Member Join Date: Sep 2002 Location: Sweden	Not quite what you want, but 2N6517/6520 from ON will at least handle the voltage and Pd required. I think it is very difficult, if at all possible, to make high-hfe devices for very high voltages.

24th February 2003, 04:31 PM	#7
OliverD diyAudio Member Join Date: Nov 2002 Location: Germany	Thanks for your suggestions... 2SA1376 + compl. is the only device that would fit perfectly from the specs, but I doubt whether it is suitable for audio... And it seems to be obsolete... Seems I have to redesign my input stage

24th February 2003, 05:26 PM	#8
Christer diyAudio Member Join Date: Sep 2002 Location: Sweden	Not that I know what design you had in mind, but a common way to deal with the problem that may perhaps be a feasible redesign in your case is to use lower-voltage transistors with high hfe and then cascode these with high-voltage transistors.

2nd March 2003, 10:14 PM	#9
OliverD diyAudio Member Join Date: Nov 2002 Location: Germany	Yup, I'll cascode the VAS and driver stages, but I don't want to cascode the input stage in this particular design. Maybe I'll just provide an additional (lower voltage) power supply, I don't know yet. Anyway, to revive this thread, does anybody know a modern replacement for 2SA1376/2SC3478? Datasheet is here: http://www.necel.com/discrete/images/pdf_e/TC-3529.pdf Also, I want to replace the famous Toshiba 2SA1145/2SC2705 as used by LCAudio. Datasheet available here: http://www.lcaudio.dk/2SA1145.pdf Can anyone help?

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