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Old 20th November 2007, 04:50 AM   #1
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Default About VAS and drivers transistors

Hello

I know that VAS transistors need to be very fast, and maby same for the drivers.

Many do use the 2SC4793 and 2SA1837, but here arround they are hard to find or fake one.

So how about MJL15032 (and MJL15033) or BD139 (and BD140), which one of those are best for VAS and drivers ?

Thank

Bye

Gaetan
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Old 20th November 2007, 04:54 AM   #2
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MJE340/350 are all good and reliable 300V/0.5A
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Old 20th November 2007, 05:28 AM   #3
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If you can find them, 2SC3423 and 2SA1360 are very good.
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Old 20th November 2007, 05:32 AM   #4
Bonsai is offline Bonsai  Taiwan
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I'm not so sure I'd use 340/350 for VAS - but for pre-driver they are ok.

I speak from bitter experience!
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Old 20th November 2007, 04:48 PM   #5
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Hello

The MJL15032 (and MJL15033) or BD139 (and BD140) are much easyer to find for me, anyone did try them for VAS and drivers ?

Btw, I live far from any cities in the north of Quebec (Canada) and mail order was always quite bad wen sent here. So wen I go to the far city I buy my stock there but they have limited kind of transistors.

And for output I can have MJ15003 (and MJ15004) or MJL3281A (and MJL1302A).

Thank

Gaetan
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Old 20th November 2007, 07:05 PM   #6
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Just about any transistor can be used for a Vas or predriver.
It's a question of what is the best transistor for this application.

Not knowing the circuit specifics makes discussion of part substitution difficult.
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Old 20th November 2007, 08:16 PM   #7
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A little bit of topic, but I try to avoid the MJL15032/33 as I have had the pleasure to have several hundred fakes of those ( each time power was turned on)
Replaced with MJL15030/31 and everything worked just perfect
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Old 20th November 2007, 08:20 PM   #8
syn08 is offline syn08  Canada
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Default Re: About VAS and drivers transistors

Quote:
Originally posted by gaetan8888
Hello

I know that VAS transistors need to be very fast, and maby same for the drivers.

Many do use the 2SC4793 and 2SA1837, but here arround they are hard to find or fake one.

So how about MJL15032 (and MJL15033) or BD139 (and BD140), which one of those are best for VAS and drivers ?

Thank

Bye

Gaetan
For the VAS, Fairchild's KSC3503/KSA1381. Mouser carries these devices for pennies. They are Sanyo's 2SC3503/2SA1381 clones.
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Old 20th November 2007, 09:31 PM   #9
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Hello

The amp will have a EF type II output Self's type.

Btw, for the output, which best; MJ15003 (and MJ15004) or MJL3281A (and MJL1302A) ?

Thank

Gaetan
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Old 20th November 2007, 10:37 PM   #10
AKSA is offline AKSA  Australia
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Myhrrhleine,

Here are the requirements:

Faster than 150MHz
Cob less than 2pF
Flat hfe from 1mA-20mA across a wide voltage range
Strong SOAR curves to resist 10-20mA with Vce of 100V
hfe up around 150 minimum

For these reasons I go for 2SC3423/2SA1360, though Syn08's choice is a good one too. I find the NPN has slightly lower Cob and higher beta.

Cheers,

Hugh
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