high voltage bjts

Stretto · 23rd July 2011, 07:46 AM

Anyone familiar with some high voltage low power bjt based amplifiers?

I'm looking for some common-emitter circuits that work with a VCC of about 400V.

I can't even find any V/I graphs to compute loadlines for them and everything I've tried has some problems clipping.

lineup · 23rd July 2011, 08:46 AM

KSP94 - 400V
http://www.fairchildsemi.com/ds/KS/KSP94.pdf

Stretto · 23rd July 2011, 09:24 AM

Um, there is no Vce/Ic graph!?!?!

sakis · 23rd July 2011, 10:54 AM

hmmmm i smell online psu .... and thread closed very soon .....

jcx · 23rd July 2011, 12:15 PM

second breakdown is the big problem with bjt you may need 2-3x rated V for any current at all in SOA - some bjt for CRT drive are still made but fewer as time goes on, some have been desinged for sw mode ps too

2SC3183

Stretto · 23rd July 2011, 12:28 PM

sakis: this has nothing to do with a psu. It is for a voltage amplifier.... i.e. the CE thing I mentioned. So you should get your nose checked...

jcx: Don't let sakis lead you astray... this has nothing to do with power. (I'm not sure what part of high voltage low power he doesn't understand)

I'm simply wanting to replace a tube fx section with a solidstate version. The cathode follower is no problem but the common cathode is. I can't find any information on do this at such a high voltage. I'm kinda pushing it in any case but I simply need some voltage amplification to drive the PI to get enough power output from the amp. (I'll use a follower after the amplifier to actually drive the PI)

I know it's not impossible to implement such a replacement circuit as I've heard of ss tube replacements.

Mooly · 23rd July 2011, 12:58 PM

High voltage low power... look at CRT line timebase output transistors. Generic types such as BU508, BUT11 etc. Low gain but would be very rugged I imagine for your application even if they didn't always seem it in TV's lol. There are countless such devices... just beware that many incorporate a high speed recovery diode (eg BU508D).

Stretto · 23rd July 2011, 01:29 PM

Mooly: I'm kinda looking for more info. Are these devices and other "high voltage" bjt's, mosfets, and igbt's used very similar to the low voltage case with just a scaling up of resistors or are their a lot of issues that makes it much more difficult?

e.g., if I have a 600V IGBT and I hook it up as a CE amp with the appropriate resistor values and bias should I expect to get a decent amplifier? (maybe somewhat non-linear but would it work or would I create a subminature black hole that will suck in my left testicle?)

CBS240 · 23rd July 2011, 02:40 PM

Quote:

Originally Posted by Stretto

Um, there is no Vce/Ic graph!?!?!

There is no derating graph either. It does state that it is complementary to KSP44, and it has a SOA plot. IMO TO-92 w/out heat sink should operate no more than 60% Pd and given the voltage in this case, <40%. 1mA @ 350V would be pushing it a bit I think. Might have to use multiple paralleled devices....

Seems strange to use a PNP device to substitute a valve. Is this some sort of feedback pair arangement?

QSerraTico_Tico · 23rd July 2011, 02:49 PM

Maybe transistors suitable for lighting ?

23rd July 2011, 07:46 AM	#1
Stretto diyAudio Member Join Date: Oct 2008	high voltage bjts Anyone familiar with some high voltage low power bjt based amplifiers? I'm looking for some common-emitter circuits that work with a VCC of about 400V. I can't even find any V/I graphs to compute loadlines for them and everything I've tried has some problems clipping.

23rd July 2011, 08:46 AM	#2
lineup diyAudio Member Join Date: Dec 2005 Location: the north	KSP94 - 400V http://www.fairchildsemi.com/ds/KS/KSP94.pdf __________________ lineup

23rd July 2011, 10:54 AM	#4
sakis diyAudio Member Join Date: Jan 2006 Location: nea makri athens greece	hmmmm i smell online psu .... and thread closed very soon ..... __________________ SERVICE ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr

23rd July 2011, 12:58 PM	#7
Mooly diyAudio Member Join Date: Sep 2007	High voltage low power... look at CRT line timebase output transistors. Generic types such as BU508, BUT11 etc. Low gain but would be very rugged I imagine for your application even if they didn't always seem it in TV's lol. There are countless such devices... just beware that many incorporate a high speed recovery diode (eg BU508D). __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

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23rd July 2011, 09:24 AM	#3
Stretto diyAudio Member Join Date: Oct 2008	Um, there is no Vce/Ic graph!?!?!

23rd July 2011, 12:15 PM	#5
jcx diyAudio Member Join Date: Feb 2003 Location: ..	second breakdown is the big problem with bjt you may need 2-3x rated V for any current at all in SOA - some bjt for CRT drive are still made but fewer as time goes on, some have been desinged for sw mode ps too 2SC3183

23rd July 2011, 12:28 PM	#6
Stretto diyAudio Member Join Date: Oct 2008	sakis: this has nothing to do with a psu. It is for a voltage amplifier.... i.e. the CE thing I mentioned. So you should get your nose checked... jcx: Don't let sakis lead you astray... this has nothing to do with power. (I'm not sure what part of high voltage low power he doesn't understand) I'm simply wanting to replace a tube fx section with a solidstate version. The cathode follower is no problem but the common cathode is. I can't find any information on do this at such a high voltage. I'm kinda pushing it in any case but I simply need some voltage amplification to drive the PI to get enough power output from the amp. (I'll use a follower after the amplifier to actually drive the PI) I know it's not impossible to implement such a replacement circuit as I've heard of ss tube replacements.

23rd July 2011, 01:29 PM	#8
Stretto diyAudio Member Join Date: Oct 2008	Mooly: I'm kinda looking for more info. Are these devices and other "high voltage" bjt's, mosfets, and igbt's used very similar to the low voltage case with just a scaling up of resistors or are their a lot of issues that makes it much more difficult? e.g., if I have a 600V IGBT and I hook it up as a CE amp with the appropriate resistor values and bias should I expect to get a decent amplifier? (maybe somewhat non-linear but would it work or would I create a subminature black hole that will suck in my left testicle?)

23rd July 2011, 02:49 PM	#10
QSerraTico_Tico diyAudio Member Join Date: Oct 2004	Maybe transistors suitable for lighting ?

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