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Old 1st August 2002, 09:42 PM   #1
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Question 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
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Old 1st August 2002, 10:27 PM   #2
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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
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Old 1st August 2002, 10:54 PM   #3
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Default 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

SOS for BJT's in output ???

Itís only the first draft so any input is welcome

Thanks

\Jens
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Old 1st August 2002, 11:30 PM   #4
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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
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Old 1st August 2002, 11:37 PM   #5
sonnya is offline sonnya  Denmark
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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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