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Old 24th August 2005, 02:15 PM   #1
sovadk is offline sovadk  Denmark
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Default looking for dual npn and dual npn smt transistors

I'm making a current feedback opamp and for that a need dual npn and dual npn smt transistors. Does anybody know any part numbers?

Thanks in advance
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Old 24th August 2005, 02:33 PM   #2
Mr Evil is offline Mr Evil  United Kingdom
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I assume you mean NPN and PNP? There are lots and lots of dual parts out there, but most of them are in really tiny packages (e.g. SOT-363) that are hard to solder by hand, such as BC846BS/BC856BS. They also come in larger packages (e.g. SOT-23-6) such as BC846U/BC856U by Infineon. Other manufacturers also make similar ones with different letter suffixes.

Fairchild make some nice ones: FMB100/FMB200. They also do a quad device (2 NPN + 2PNP) MMPQ6700, which is great for where thermal matching of four devices is desireable, although the transistors aren't so great for their individual specs.
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Old 24th August 2005, 02:47 PM   #3
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BC847/57 is quite nice and dirt cheap.... but real small. I have used those in my monster vinyl amp QSXM2 and in my monster headphone amp QRV-01. The most positive thing in a differential input stage is the temp matching rather than the electrical matching which is rather unspecified.

If you are after extremely low noise and matching maybe SSM2220 anndSSM2210 may suit your needs.
http://www.analog.com/en/prod/0,2877,SSM2220,00.html
http://www.analog.com/en/prod/0,2877,SSM2210,00.html
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Old 24th August 2005, 09:41 PM   #4
sovadk is offline sovadk  Denmark
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Size dosn't matter. I'be been looking for suppliers of bc846s, bc856s, but been unable to find any that ships less than 1k+ devices. Do you know any? (I live in Denmark by the way).

I want the pairs mainly because of thermal matching, but the enclosed low vbe dispersal is also a plus. Any par will probably do fine. Accessibility seams to be the main concern.

My applicating is the input stage of a self osscilating class d afmplfier. The transistors are to work with a vce of 40 volts, so this vbss should be larger than this.

I have a whole bunch of pumt1, pumz1 anf pumx1 (Philips) pairs, but their vbss is only rated to 30 vols. I've used these devises in simulations and reduced their vce with two cascode couplings. They work very well in this configuration, but devices with a higher vbss rating would simpliy things a bit.
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Old 24th August 2005, 10:12 PM   #5
Mr Evil is offline Mr Evil  United Kingdom
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Farnell have them and I think they should ship to you.
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Old 25th August 2005, 03:27 AM   #6
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Hi peranders ! I haven't ever bought tst through internet .
http://www.analog.com/en/prod/0,2877...,00.html#price
If I buy 1000 unit ---> total money must be pay is 2.73$ or 2.73$ /1 unit ?
thanks !
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Old 25th August 2005, 04:13 AM   #7
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Default Re: looking for dual npn and dual npn smt transistors

Quote:
Originally posted by sovadk
I'm making a current feedback opamp and for that a need dual npn and dual npn smt transistors. Does anybody know any part numbers?
Zetex also makes some. Check their web site:

http://www.zetex.com/3.0/b1-21.asp
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Old 25th August 2005, 06:01 AM   #8
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Try these:

http://www.el-supply.dk/
or
http://www.elfa.se/dk/

regards
Ole
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Old 25th August 2005, 06:30 AM   #9
sovadk is offline sovadk  Denmark
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Farnell has bc846s but not bc856s I might be able to use bc857s instead, but the vbss is critically low.

I can see that Rohm's making a lot of dual transistors :
http://www.rohm.com/products/shortfo...tr_index7.html
IMT4 (2SA1514K×2) and IMX8 (2SC3906K×2) seams interesting, but I can't find anything about noise figures. Do you guys know anything about these devices?

Til Ole
El-supply don't have any dual transistors and Elfa only have the bc8?7 series with a voltage rating of 45Vce. But thanks anyway.
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Old 25th August 2005, 10:58 AM   #10
sovadk is offline sovadk  Denmark
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I just found DMMT5401 and DMMT5551 by Diodes Inc. They are mached, have a noise figure of 8dB and can be bought for 0.4$ each at mouser.com
They are the same as Fairchilds FMBS5401 and FMBS5551 although these are not mached down to 2% with respect hfe and vbe as the Diodes Inc. parts are.

DMMT5401
DMMT5551
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