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Substitute transistor.

Discussion in 'General Electronics Discussion' started by sureshot, Mar 1, 2016.

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  1. sureshot

    sureshot

    234
    13
    Jul 7, 2012
    Having a look for another decent psu circuit i found this in the image below. Problem is i am having problems finding a BD131 NPN transistor.
    I was wandering if anyone can help with a substitute, thanks for reading, any help appreciated.
    Having a few ideas like the BD437 but not completely sure.
     

    Attached Files:

    Last edited: Mar 1, 2016
  2. davenn

    davenn Moderator

    14,003
    2,025
    Sep 5, 2009
    not to put you off too much, but the 723 regulator is a very old and dreadful to use regulator chip

    you would be much better going to LM338 style .... just a suggestion :)


    Dave
     
  3. 73's de Edd

    73's de Edd

    3,365
    1,406
    Aug 21, 2015
    .

    Sir Sureshot . . . . . . .

    I always used to utilize a TO-66 cased 2N3054 in those regulator strings as the first driver, and the little brother of TO-3 cased 3055's..

    The specified BD131 specs out with:

    Collector to base voltage 70V
    Max collector current 3A
    Power dissipation 11W
    Beta 40

    Here is a whole page of that 2N3054 power NPN family, plus newer / others that even excell its specs.

    https://www.centralsemi.com/PDFs/selection/leaded/PT_TO_66Case.pdf

    I still like that LM 723, for its holding tight load to unload regulation capabilities as well as just regulating to a wide voltage input swing, plus its ADJUSTABLE foldback current limiting you see being involved on its pin 2..
    Before that "old " part, which was a many, many year industry standard for a linear supply voltage chip (or shunt also ) I even used the forerunners top hat LM304 and LM 305's.
    Before that, it was being MULTI discrete parts design.


    73's de Edd
     
    SOLARWIND likes this.
  4. sureshot

    sureshot

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    Jul 7, 2012
    Thanks Davenn. I have built an lm338K and an lm338T version linear regulator supplies. I was moving towards the more challenging circuits, not just for there PCB layout but also unit constructional layout. I've never used the 723 Regulator, but though I'd give it a go.

    Retail psu's I've looked into in the past look like they use it, or a variant off it. I'm always looking for new psu circuits, so if one pops up with a different regulator or IC at the heart of it I may go with that instead.
     
  5. sureshot

    sureshot

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    13
    Jul 7, 2012
    Thank you Edd. I will have a look at your surggestion, of the 2N3054, and thanks for the link ! Always a pain in the back side when you find a circuit, only to be challenged by obsolete of hard to find parts lol.
     
  6. sureshot

    sureshot

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    Jul 7, 2012
    Thanks for your help here, a bit more searching and I've managed to pin down a supplier with the BD 131 transistor, thanks again all.
     
  7. AnalogKid

    AnalogKid

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    Jun 10, 2015
    There is nothing wrong with using another 3055 as the darlington driver.

    ak
     
    SOLARWIND likes this.
  8. sureshot

    sureshot

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    Jul 7, 2012
    Yes it certainly powerful enough, it achieves the Darlington configuration, and the HFE is about there almost. But as I can get the BD131 for £0.80 its not to bad. Thank you for the tip ! Appreciated.
     
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