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-   -   BJT for VAS (http://www.diyaudio.com/forums/solid-state/4956-bjt-vas.html)

JensRasmussen 1st August 2002 08:42 PM

BJT for VAS
 
For my amp I need to find transistors for the VAS

I'm thinking about the pair mje340/350, but not really sure if they are the best ones for the job.

The rails are +- 65 V , so the transistors must be rated at atleast 130 V CE.

What other devices are out there ?

Thanks

\Jens

JonMarsh 1st August 2002 09:27 PM

I've used the 340/350 in the past to good effect, particularly as cascode transitors and predrivers.

You might want to take a look at the Zetex FZT696 and FZT796, if you don't mind surface mount SOT223; 180 and 200V, very good gain and gain linearity, low capacitance.

Regards,

Jon

JensRasmussen 1st August 2002 09:54 PM

Transistors
 
Hi

Well I would prefer leaded devices (spelled right I hope) since the boards are going to be made at my school by me ;-).

About the mje340/50 do you know the FT of these? Iím using devices from ON, but their datasheet does not give this info.

Also the power must be about 5 W so I can use different quiescent currents for the VAS.

Iím planning to use mje340/50 for predrivers, is this ok ?

Please se the schematic at

http://www.diyaudio.com/forums/showt...5&pagenumber=2

Itís only the first draft so any input is welcome

Thanks

\Jens

rtirion 1st August 2002 10:30 PM

You might like to take a look at

2sa1209 PNP and 2sc2911 NPN from Sanyo
Vceo=160V,Pc=10W,Ic=0,14A,Ft=150Mhz

Regards

sonnya 1st August 2002 10:37 PM

Still look at Zetex... They are faster (~100MHz) most of the the time.. Better Gain linearity and FZT should have replacements in a leaded house They are called ZTX...

ZTX453 and 553 are good ones but not more than 120V if i am right...

Go look at www.zetex.co.uk (Good old brit's)


Sonny


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