BJT in IC package

Discussion in 'The Projects Forum' started by justin8282, Feb 28, 2010.

  1. justin8282

    Thread Starter New Member

    Feb 28, 2010
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    hi, i'm newbie in this forum.
    i want to ask bout transistor.
    is that any suggestion for me to find a IC package with npn inside such as 7408 got 4 AND gate inside?

    best regard,
    justin
     
  2. hgmjr

    Moderator

    Jan 28, 2005
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    They are referred to as transistor arrays. Here is a link to a quad-transistor IC I found at www.mouser.com.

    hgmjr
     
  3. justin8282

    Thread Starter New Member

    Feb 28, 2010
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    thx 4 the info yea...

    regard
    justin
     
  4. gimpo

    Member

    Jan 27, 2016
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    I resume this old post.
    No way to find a dual BJT in IC package?

    I have to realize a couple of circuits like the following (two NOT-gate, I suppose):

    iso_transceiver.jpg

    The author suggests the use of two 3904 BJT but the vertical size is remarkable in the version with bent leads (around 7mm!) :(
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Hallo gimpo... this should have been a thread on it's own but here we are...

    Can you give a better description of the size of the circuit? A picture or sketch would be of great help (and need not be translated).
     
  6. gimpo

    Member

    Jan 27, 2016
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    Hi Ernie. Maybe you're right, now my question seems weakly related to the previous one...

    I'm going to design the PCB from the scratch using Eagle software.
    The max height of the component on the board surface should be around 6mm (0.24"). In any case, since the board has to be mounted on a motorcycle I would avoid to use tall components 'cause of vibrations.

    Unfortunately I have no experience in soldering SMD ICs, so I was searching for a low profile chip mounted through holes.
    Somewhere I've read that the same circuit could be realized by using 2N7002 MOSFETs, but:

    1. I have no if dual ICs are available for that transistor,
    2. I have no idea the right value of resistors.
     
  7. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Include voltage of DLC if you can.
     
  8. #12

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    Nov 30, 2010
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  9. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    I'd just stick with a transistor since we don't know what else is in the circuit (what drives it/what it drives).

    A 2N3904 is as good as any other device here. Actually, finding an NPN transistor that would not work here would be difficult.

    If you get a 2N3904 in the plastic TO-92 package you could mount it on it's flat side where it is just a shade over 4mm tall maximum.


    Data sheet, size on page 9:
    https://www.fairchildsemi.com/datasheets/MM/MMBT3904.pdf
     
  10. ErnieM

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    Apr 24, 2011
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  11. SLK001

    Well-Known Member

    Nov 29, 2011
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    Why not use a 3904 in a SOT23 package? I've also see twin transistors in a SOT23-6 package.
     
  12. gimpo

    Member

    Jan 27, 2016
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    A lot of answers and tricks! :)
    I will take a moment to examine all the proposed ideas before posting further.
     
  13. gimpo

    Member

    Jan 27, 2016
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    I apologize for the poor information I gave.
    Accordingly to ISO-9141-2 and ISO 14230 standards the output of those two circuits are in the range [0 Volt, +12 Volt] whereas the 0 Volt is logic level low and +12 Volt is the logic level high.
    The two Input signals comes from an STN1110 IC working with TTL 3.3V logic levels.

    Yeah, the 2N3904 is quite good for my application, I thought to mount it with bent leads. Maybe it's the best solution... but I would like to have a more "clean" layout on the board and that bent transistor take a lot of space on the surface.

    It seems strange to me that not a DIP package is available on the market. On the hand, there is a wide choice of MOSFET arrays IC.s
     
  14. gimpo

    Member

    Jan 27, 2016
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    I apologize again. :oops:
    As posted above, DLC is acronym for "Diagnostic Link Connector" (i.e. the OBD adapter going to the OBD connector of a car/motocycle). It carries +12 Volt from the vehicle's battery (filtered and stabilized).
     
  15. gimpo

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    Jan 27, 2016
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  16. gimpo

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    Jan 27, 2016
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    Uh! Nice to see you again SLK001 :)
    I would not go for SOT23 package 'cause I feel still not enough confident with SMD soldering. :oops:
     
  17. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    They briefly refer to those as "freewheeling diodes" in the data sheet, and since they spec the performance they are legitimate to use, mostly for circuits where the load can spike negative. These "catch" that spike from going very negative.

    I doubt your circuit has such a need, and the presence of these diodes will not change how your circuit works one bit.
     
  18. gimpo

    Member

    Jan 27, 2016
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    The chip has overdimensioned BJTs (400V and 8A dc current max, wow!) but anyway it is ok for my needs. I would say that the search for a dual BJT in DIP package is over!

    A fresh beer for you all guys! :D
     
    ErnieM likes this.
  19. #12

    Expert

    Nov 30, 2010
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    They are an inherent part of the chip, sort of a parasite caused by using a substrate for more than one device. The good part is that they are facing the right way for the transistors to work.;) If nobody had drawn them, you wouldn't have noticed.:p

    Same thing goes for op-amps, digital logic chips, and mosfets. They all have a , "body diode". It's the nature of Integrated Chips and it's the first reason they smoke if you connect the power supply backwards.:eek:
     
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